Based on arithmetic theory and numerical performance regularity， this paper analyzes the reason why the computation of continuation power flow（CPF） may encounter convergence problem in the iterative correction process close to the turning point of the solution parameter curve.As a result， based on the normalized predictor tangent vector， this paper presents an improved local parameter selection strategy， which can reduce the possibility that the calculation may not converge， to improve the robustness of CPF. At the same time， in order to solve the problem that some initial parameters should be confirmed through trial and error process in engineering applications， this paper advances an automatic variable step size controlling algorithm using correction iterative times as its main parameter. Simulations on IEEE 39-bus system and Shandong Power Grid typical operation ways in the winter of 2010 verify the effectiveness of the improved method.