This paper analyzes the no-load and heavy load power supply of long distance 10 kV runthrough electric power line. When no-load

the terminal voltage of the line is increased

but it is very small

which has little influence on the power supply. The article focuses on the analysis of the phenomenon that the terminal voltage drop exceeds the specifications criterion during heavy load in long distance 10 kV run-through line

and puts forward a scheme for setting up series capacitor compensation.It is found that in the design process designers always pay close attention to the voltage end of the line

but pay no attention to the voltage of the line where mount the series capacitor equipment. At last the problem is analyzed by simulation

and the method and idea of solving the problem are put forward.