Power system state estimation is the basis of advanced power application functions. As static fundamental data, network parameters have a lasting impact on the credibility of state estimation results. Presently, experiences from daily state estimation maintenance show that, the accuracy of reactive power and voltage estimation results is usually worse than the accuracy of active power estimation results. Based on detailed analysis of transmission line resistance parameter’s impacts on reactive power estimation results, this paper points out that, if only resistance parameter is changed, transmission line’s reactive power injection of both sides should be changed with same amount in opposite direction. Furthermore, this paper proposes a solution when reactive power measurements contradict to the state estimation results. Examples in actual power system are given to demonstrate the accuracy of the analysis conclusion proposed by this paper.