In the actual microwave thermo-induced ultrasound imaging, the ultrasonic point sources excited by the microwave pulse are highly dense. Hence, we do some research work on using the MUSIC algorithm to address this issue because the MUSIC algorithm has high spatial resolution, which can estimate signal parameters in multipath propagation and high density signal environment well. The idea of robust Capon beam-forming is used to avoid the performance degradation of the standard MUSIC algorithm. We first estimate the true value of the steering vector and then apply it to Standard MUSIC algorithm. We also analyze of the accuracy of restoring the tumor imitation and the ability to suppress noise. The results demonstrate that the improved algorithm can estimate the spatial spectrum well, and can improve the quality of microwave thermo-induced ultrasound imaging.