Abstract: Major oil and gas reservoirs in Xihu Sag developed in Pinghu and Huagang formation. Organic matter of Pinghu source rocks is of type III, and main hydrocarbon type in Xihu Sag is gas reservoir (condensate gas reservoir) and light oil reservoir, which is characterized by high fluidity and high volatility. At present, several logging methods have been used in Xihu Sag, in which gas logging can evaluate the hydrocarbon type initially while drilling. Meanwhile, geochemical logging and quantity fluorescence test are not so effective as gas logging in hydrocarbon evaluation.