As a new pile foundation, the crew pile has been used in civil engineering, roads and bridges, etc. because of its good bearing capacity, but recently the bearing mechanism of screw pile has not been studied deeply. In order to study the bearing mechanism and calculation method of bearing capacity of screw pile, under the foundation of previous research work, through theoretical analysis, we investigate the vertical bearing mechanism of the screw pile, analyze the calculation method of bearing capacity when the ultimate bearing capacity has not reached the ultimate capacity, and gain the calculation formula of the resistance of pile segment and the vertical ultimate bearing capacity, which provides a theoretical support for further study and application of the screw pile.