Regarding surface emitting distributed feedback (SE-DFB) semiconductor laser as the research object, this paper investigates the controlling effects of second-order gratings on the emission characteristics of the laser characterized by the coupling coefficient in light of the coupled-mode theory. The finite-difference time-domain (FDTD) method is used to simulate the grating structure and optimize the grating parameters. The distributed Bragg reflector (DBR) is introduced onto the substrate of the laser to coordinate with the gratings to control the emission characteristics. With a 980 nm semiconductor laser, this paper focuses on the comprehensive influences of various parameters on the grating coupling coefficient to obtain the optimal grating parameters. Those parameters include DFB grating duty cycle, length of DFB grating period, etching depth of DFB gratings, tooth angle of DFB gratings, duty cycle of the DBR reflector, material refractive index of the DBR reflector, and number of period medium layers of the DBR reflector. This research provides a theoretical basis for the design and fabrication of subsequent devices.