To analyze the impact of transmitting nonideal quadrature signal on FDA (frequency diversity array) beamform, based on the signal model of FDA, the orthogonality issue of baseband signal was brought out, the beamform expression was deduced mathematically under the condition that FDA system transmitting nonideal orthogonal baseband signal, and the performance of matched reception processing was further analyzed. Based on the calculation amount of beamform transmission and matched reception of FDA system, the influencing factors were extracted, and a quantitative analysis of the relationship between the orthogonal characteristics of the baseband signals and the performance of the beamform and matched reception was constructed. Based on the numerical simulation of six kinds of typical random distribution biphasic coded baseband signals, the correctness of theoretical analysis was verified by experiments. Different random distributions show different baseband signal orthogonal characteristics, and their influence on the performance of FDA beamform transmission and matching reception varies with the orthogonal characteristics. From the perspective of orthogonality, the application potential of baseband signal based on Normal, Uniform and Logistic random distribution is better.