The oceans have a large amount of unexplored resources, so the exploration area of human beings is moving towards the unknown ocean as land resources are getting scarce. Underwater wireless optical communication technology with higher rates and better security has become the key to underwater environmental monitoring, wireless sensor networks, offshore exploration and communication between submarines. Vortex beams are a class of beams with helical phase wavefront carrying Orbital Angular Momentum (OAM), which have been widely used in the fields of optical communication, remote sensing and super-resolution imaging due to their specific helical phase structure and dark hollow ring light intensity distribution. The transmission of vortex beams in seawater environments is interfered by ocean turbulence, which results in light intensity scintillation, phase undulation and spot drift, which can degrade the communication quality. However, as human activities extend from free space to the marine environment, the demand for the communication capacity of underwater optical communication systems is increasing, so it is of great significance to study the coded communication of underwater vortex beams and their superposition states, and to further explore methods to suppress the effect of ocean turbulence on the transmission of the beams, for the underwater vortex optical communication systems.In this paper, power spectrum inversion method are used to establish a phase screen model of ocean turbulence, simulate real ocean turbulence, and study the light intensity and phase characteristics of Double Laguerre-Gaussian Vortex Beam (DLGVB) generated by coaxial superposition during transmission in ocean turbulence. The scintillation index of DLVGB beam under different ocean turbulence parameters and topological charge difference is simulated and analyzed. According to the scintillation index, the bit error rate of the underwater optical communication system based on On-off Keying (OOK) modulation under different ocean turbulence parameters is further calculated, and the bit error rate of the optical communication system under different topological charge difference is simulated and analyzed.The results show that the scintillation index of Double Laguerre-Gaussian Vortex Beam (DLGVB) increases with the decrease of turbulent kinetic energy dissipation rate, the increase of transmission distance, salinity temperature fluctuation equilibrium parameter and temperature variance dissipation rate. The main reason is that the intensity of ocean turbulence will gradually increase with the decrease of turbulent kinetic energy dissipation rate and the increase of salinity temperature fluctuation equilibrium parameter and temperature variance dissipation rate. Compared with the traditional Laguerre Gaussian vortex beam, the DLGVB beam with lower topological charge difference (v<10) can maintain relatively stable and low scintillation index in the environment with the increase of ocean turbulence intensity, and the scintillation index shows a trend of decreasing, then increasing and finally decreasing with the topological charge difference of the DLGVB beam, which is related to the number of splitting points of the beam and the dispersion of the energy; for the underwater vortex optical communication system, the BER decreases with the increase of turbulent kinetic energy dissipation rate and the decrease of temperature variance dissipation rate and salinity temperature fluctuation equilibrium parameter; the BER is lower when the temperature is dominant and higher when the salinity is dominant, so the communication performance is better when the temperature is dominant in the oceanic turbulence; when the topological charge difference is lower (v<10), the communication performance of DLGVB beams with different topological charge differences is better. When the topological charge difference value (v<10) is low, the communication BER of DLGVB beams with different topological charge difference values decreases with the increase of the signal-to-noise ratio, and the BER of DLGVB beams with a large topological charge difference value is smaller than that of DLGVB beams with a small topological charge difference value, so that DLGVB beams with a large topological charge difference value are selected to have a better quality of communication when the topological charge difference value (v<10) is low.Under the ocean turbulence environment, the use of DLGVB beams for transmission can effectively suppress the interference caused by ocean turbulence; when analyzing and designing the underwater optical communication system, combining vortex beams and their superposition states with the underwater optical communication based on OOK modulation, and selecting the optimal topological charge difference, can effectively improve the transmission and communication quality as well as the capacity of the communication system. The research results of this paper have important reference value for the study of transmission characteristics of vortex beams and their superposition states under ocean turbulence, as well as for the development needs and applications of continuous capacity expansion of underwater optical communication systems based on orbital angular momentum.