Abstract: In Xihu sag of East China Sea basin, the gas saturation evaluation for low-permeability tight gas reservoirs is always the key difficulty in exploration and development. The conventional core analysis method such as mercury injection is difficult to get accurate gas saturation of low-permeability tight gas reservoirs. Compared with conventional core analysis, the measured water saturation through sealed coring is more approaching to the actual situation. But water volatilization is a problem. In order to accurately calibrate the gas saturation, the paper analyzes the main factors influencing the water saturation through sealed coring, compares 3 core treatment methods, proposes a new water saturation correction method considering the distortion of rock pores and based on the experiment of sealed-coring volatile quantity of low-permeability tight gas reservoirs, and performs water saturation correction through sealed coring in WELL-5 in Xihu sag with the total correction of about 10%. The results show that the new correction method is simple and practical, which is suitable for the sealed coring saturation correction for low-permeability tight gas reservoirs in Xihu sag of East China Sea basin