In recent years, the Permian and Triassic marine carbonate strata of Sichuan Basin have found Puguang,Longgang, Yuanba and many medium-size, high porosity and permeability gas field, and these natural gas is mainly oil cracking gas. Porosity would be a key factor in controlling paleo-oil accumulation on condition that the oil source was sufficient, the discussion of threshold value of paleo-oil charging has guiding significance, especially for the tight carbonate reservoir. Changxing-Feixianguan formations in northeastern Sichuan basin found a lot of solid bitumen, which were mainly filling in sparry oolitic limestone interparticle pores, crystalline dolomite intergranular pores and residual oolitic dolomite moldic pores, and rarely observed post-bitumen cements. In this study, the solid bitumen content and present porosity were quantified, and their sum was approximately visual paleo-porosity; The relationship between bitumen content and present porosity, bitumen content and visual paleo-porosity were discussed respectively, and the visual paleo-porosity threshold was determined; Finally, through the proofreaded and corrected of compaction ,the porosity threshold for paleo-oil accumulation was obtained. The results reveal that solid bitumen content was irrelevant to present porosity, while a positive relationship with visual paleo-porosity, which significantly increased above 1.0% when visual paleo-porosity was above a certain value; The porosity threshold value of Puguang gas field Changxing and Feixianguan Formations, Yuanba gas field Feixianguan Formation and Jiannan gas field Feixianguan Formation were 6.4%~7.4%（average 6.8%）.