In the calculation of oil reserves of paleo oil reservoirs, the area of paleo oil reservoirs is generally determined according to the distribution area of asphalt or according to the area of paleo traps. These methods have limitations. In view of the defects and deficiencies in the existing methods for determining the petroleum reserves of paleo oil reservoirs, considering the Sinian Dengying Formation gas field of the Anyue gas field in the Sichuan basin as an example, the calculation formula of paleo oil reservoirs was established.At the same time the relationship between paleo oil reservoir area and current gas reservoir area, and the relationship between paleo oil reservoir porosity and current gas reservoir porosity was established. Taking into consideration multiple parameters of the current gas reservoir, including gas bearing area, reservoir physical properties, gas saturation, original gas deviation coefficient, formation temperature, the formation pressure of gas reservoir, natural gas density, and the oil density, oil volume coefficient and asphalt density of similar oil reservoirs, oil reserves of paleo oil reservoirs were quantitatively calculated according to the law of material conservation, which improved the reliability and accuracy of the results. This will provide a new idea for the reserve recovery of paleo oil reservoirs in marine high over mature areas in China. At the same time, the reserve recovery of ancient reservoir is of great significance to reproduce the dynamic evolution process of reservoir formation.