Overhead conductors’ thermal and mechanical states are the critical factors to determine their safe operation and have an impact on the power flow calculation. The thermal and mechanical state parameters of overhead conductors change the resistance parameters of the line on the one hand and change the line parameters through the tensile action of force on the line on the other hand. The parameters of the line are closely related to the power flow calculation of the power system. Based on two kinds of influence mechanisms and regional power systems, this paper quantitatively analyzes the influence of thermal state and mechanical state on power flow under light load and heavy load.