It is the consensus of international scientific community that the greenhouse gas emission, which is caused by the human activity, leads to the global warming. In order to stabilize the CO2 content of the air to be a reasonable value, human need to decrease the CO2 emission. The enormous saline aquifer in the deep layer of the sedimentary basins, which is not appropriate for development and utilization, has a great potential to storage the massive CO2. But the specific storage capacity estimation method has not been developed completely. Based on the research and action mode of every CO2 sequestration mechanism in saline aquifer and combined with the researches of the calculation methods of foreign saline aquifer sequestration projects, this article: (1) builds a saline aquifer storage capacity calculation mathematic model; (2) based on the calculation result, analyzes the relationship between important factors, such as CO2 density, dissolved mass fraction and formation water density, and temperature, pressure and salinity; (3) determines the important factors of storage capacity and set up a quantitative relationship formula; (4) puts forward two calculation methods according to two different storage mechanisms. All in all, this article provides a technical support and specific feasible calculation method for the saline aquifer CO2 storage capacity for the storage capacity estimation of china sedimentary basins.