In the situation of the total reactive compensation capacity is definite, the minimum negative sequence current exists when the different distribution of compensation capacity at the compensation ports. Namely, the optimal configuration of the fixed compensation exists when the different distribution of compensation capacity at the compensation ports. The mathematic model of optimal configuration of the fixed compensation is established, and the optimal design of the compensation capacity is performed by using the theory of generalized Lagrange method of multipliers. The effectiveness is proved by site measurements of traction substation.