For the reasonable series reactance rate in capacitor of substations, the full parametric harmonic circuit and model for 220 kV and 110 kV substations are established, which consists of short impedance, transformer, capacitor, load, and harmonic source, and the resonance objective function that reflect the degree of resonance such as harmonic voltage amplification factor on load bus, etc. is given. With minimax optimization, the maximum values of objective function in all the power grid parameter space are minimized by changing reactance rate, and the technical and economic characteristics of the reactance rate of the capacitor are analyzed. The calculation results show that resonance is eliminated with best effect and generality by the rate 12%; resonance is eliminated with second effect by rate 4.2% ~ 4.5%, but the rate 4.2% ~ 4.5% one has better technical and economic value and is suitable for most of 220 kV and 110 kV substation.