The characteristics of the crystal field in A3B type compounds with A-15 structure are considered, the relative displacements △E⊥ between d-electron energy levels for atom A are calculated according to the pair potential model, and an improved RCA energy band model is further suggested based on the LCAO method. By following this approach, the dependence on △E⊥ of the superconducting critical temperature of the V3B compounds is obtained. The theoretical results are in rough agreement with experimental data.