Abstract: An immune algorithm is presented for the research on pattern synthesis in thinned array.Aiming at the structure of the rectangular plane thinned array,an array location factor is presented as a new factor with the form of Kronecker product.As a result,the amount of the computation is reduced while the speed of operation is improved.The immune algorithm is improved through the use of adaptive clone and Gauss immutation so as to overcome the blind search of the algorithm.As a result,searching efficiency is advanced.For optimizing the sidelobe of the rectangular plane thinned array,a binary immune algorithm and a real immune algorithm are applied to optimize element distribution and their excitation amplitude respectively.The results show the flexibility and effectiveness of the immune algorithm,and the optimal result applying immune algorithm is obviously better than the one using genetic algorithm.The proposed result shows a better characteristic of global convergence.