The industry design standard of tower foundation in China, DL/T 5219-2005 “Technical Regulation for Foundation Design of Overhead Transmission Line” is under revision, of which the parameters A1 and A2 in shearing method of tower foundation uplift calculation are specially covered. Based on the analysis of three kinds of theoretical calculation models for typical foundation uplift at home and abroad, the unified calculation model and theoretical formula for the uplift bearing capacity of tower foundation are built, the unified theoretical formula of parameters A1 and A2 for shearing method of foundation uplift calculation at different soil failure plane morphology is presented, as well as the relationship between the values of A1 and A2 and soil failure plane morphology, internal friction angle, the ratio of uplift resistance depth to diameter of foundation slab is analyzed. The research results will provide references for the engineering design of tower foundation and the formulation or revision of relevant technical specifications.