South China Sea is one of the significant marine development areas in China. It is very important to evaluate scientifically the marine engineering geological conditions on the basis of research on various factors for geologic hazards. The potential factors for geologic hazards are the essential causes of geologic hazards. They not only affect the process of marine oil exploration and development, but also cause a lot of unexpected economic loss in submarine engineering operations. This paper studies the types, size distribution, formation process, and inducing factors for possible geolgic hazards, on the basis of practical surveys in South China Sea more than 20 years. The practical measures for preventing geologic hazards are suggested in order to provide a foundation for the development of sea resources.