Underwater laser-induced breakdown spectroscopy (LIBS) and underwater laser Raman spectroscopy have been successfully applied in deep sea research. These two technologies have similar devices and complementary detecting targets. The combination of these two technologies is expected to be an improvement for deep-sea study. In this paper, a prototype of a combined underwater LIBS-Raman detection system was developed. The whole system was integrated into a pressure housing of L790 mm×Φ270 mm with two optical windows and water proof connector at the end cap. The underwater pressure vessel connected the deck control terminal with a water proof cable, through which power supply, system control, and signal delivery were provided. The main components inside the pressure vessel included a pulsed laser, two spectrometers, an embedded computer and power supply conversion devices. A dual-wavelength pulsed laser was used as the same excitation source for both LIBS and Raman spectroscopy. The 1 064 nm wavelength was used for LIBS excitation and the 532 nm wavelength was used for Raman spectroscopy excitation. The laser was split into two paths based on wavelength and illuminate to sample through different quartz window. The produced LIBS and Raman signals were collected by back-scattering optical set-up and coupled into the AvaSpec-ULS2048 and QE65000 optical fiber spectrometer respectively. Experiments have been carried out with calcite samples in laboratory, and the results showed LIBS and Raman spectra could be obtained simultaneously for solid samples. Field experiments were also carried out at the Qingdao coast, and the results proved the feasibility of developing a combined LIBS-Raman system for underwater detection. It is hoped that this prototype could be used in hydrothermal area detection in the near future after further optimization.