In this paper, an efficient algorithm is developed to analyze the steady state response of a nonlinearly loaded antenna array under multitones excitation. The problem is equivalent to a multiport nonlinear microwave network problem with the network parameters of antenna array obtained by the moment method. The antenna array mutual coupling effects are included in the equivalent multiport network. This resulting equivalent network is then solved using an efficient successive over-relaxation algorithm. Numerical examples are shown to illustrate the capability of the proposed method and the intermodulation effect of the nonlinear loads. The proposed method is suitable for nonlinearly loaded antenna array under multitones excitation.