Abstract: The sidelobe of an array antenna with self-locating structure is analysed in this paper.The expressions are derived which relate the cumulative probability of sidelobe to the range of three-dimensional element position errors,subarray position errors and a phase error in each element.The effect of scanning angel on the sidelobe of an arrays antenna is indicated.In the condition of the same position errors,the computation and simulation results show that the cumulative probability of sidelobe level of an array antenna with subarrays is different when the array has different forms.