Abstract: In this paper，a derivation shows that the uniformly-spaced array antenna pattern can be expressed as a Chirp z-transform format. Meanwhile，the Chirp z-transform can be computed with multi-FFT operations which means the Chirp z-transform can be directly used to fast compute array antenna pattern. Difference with FFT algorithm，Chirp z-transform is not troubled with the element distance. The computation result with Chirp z-transform can fitly full of visible space. Moreover，Chirp z-transform can equally get val? ues from the visible space at any numbers which increases the resolving accuracy in pointer. In the text，two examples have been given to verify the accuracy and rapidity of the Chirp-z method，and the results show Chirp-z method satisfy our requirement.