For analyzing the resolution performance of Multi-Input Single-Output (MISO) array radar with stochastic signals, the average ambiguity function (AAF) was introduced from the viewpoint of statistical theory. The analytic expression of AAF of array radar is derived. Comparisons are implemented for different modulated waveform. Numerical simulated results illustrate that the resolution performance in range and velocity is better for the stochastic frequency modulated waveform comparing with stochastic amplitude modulated or stochastic phase modulated waveforms.