The features of micro-pore throat in high pressure and low-permeability sandstone reservoir of deep section were analyzed by using the constant-rate mercury injection technology. The research shows there are little difference in the pore’s sizes and distribution, the pore radius is unimodal distribution, and the main peak is from 100 μm to 300 μm. Throat radius is the main factor that controls the reservoir property. The relation between the permeability and the throat radius is better than that between it and the pore radius. There is better correlation between the reservoir property and the pore throat parameters such as the effective throat radius, pore radius, throat volume, pore volume, and pore-to-throat radius ratio.