During 1985-1988, characteristics, distributions, genesis and correlation between some geohazards factors were investigated in west part of the northern South China Sea. There are various geohazards factors or unstable factors on sea floor in west part of the northern South China Sea, such as submarine active sand dune, tidal current sand ridge, pockmark, submarine steep-slope and scarp, continental shelf marginal valley, mud flow, submarine erosion and erosional residue hill, buried paleo-channel, buried paleo-lake, buried paleo-delta,marsh-gas and shallow high pressure gas, slump fault and active fault, submarine landslide. According to their locations and hazardous effect, geohazards factors can be divided into two categories:sea floor geohazards and underground geohazards. The former is of geomorphological and geologioal nature, endangering submarine constructions on sea floor. The latter is exclusively of geological nature. Based on the latency and dangerous degree of hazards, each category of geohazards factors could be divided into three types: immediate hazard factors, latent hazard factors and constraint hazard factors. The investigated area can also be divided into various geohazard zones as follows: immediate sea floor hazard zone, latent sea floor hazard zone, immediate sea floor constraint hazard zone, sea floor basically no hazard zone, immediate underground hazard zone, latent underground hazard zone, underground constraint hazard zone and basically no hazard zone.