Abstract: In 1930's,German Laubmeyer and former Soviet Sokolov developed gas surveying method,raising the curtain on petroleum geochemical exploration.Up to now a whole series of methods and indicators have been set up so as to detect the physical,chemicalandbiologicalchanges related to hydrocarbon microseep in surface environment.The experimental analysis techniques used to detect micro petroleum information near surface have been considerably developed.The reliability of evaluating deep oil and gas prospect according to the surface geochemical anomaly has been greatly improved.The hydrocarbon-bearing interval,buried depth and scale of an oil and gas accumulation can not be accurately determined by surface geochemical exploration as yet.However,the expleration practice at home and abroad has proved that by using petroleum geochemical prospecting methods,good results in regional oil-and gas-prospect evaluation,direct detection of hydrocarbon in a trap as well as optimizing drilling targets were achieved.Surface petroleum geochemical prospecting is an effective oil and gas exploration means being supplemental to conventional petroleum geologic and geophysical methods.According to the existing research and application achievements,combining oil and gas geochemical techniques with the conventional petroleum exploration methods can play a certain role in the whole processes of petroleum exploration and development no matter in land or in ocean.Surface oil and gas geochemical exploration has characteristics and advantages of low-cost,short-period and directness.This technology will play an increasingly important role in oil and gas exploration in the coming dozens of years along with the research being deepgoing and unceasing innovation of methods.