Microwave-induced thermoacoustic imaging is a noninvasive, high contrast, high resolution, and cost effective method for cancer detection. It has the potential to serve as a routine breast tumor screening. In the present study, simulation and experiment have been used for pulsed microwave energy spatial distribution investigation. The target to be imaged is a 99 square array composed of tubes 3 mm in diameter and 8 mm in separation. The simulation and experimental results both indicat that far away from the antenna, more tubes could be thermoacoustically recovered, which means a larger radiation area obtained. The thermoacooustically recovered tubes are 3.1 mm in diameter and 7.7 mm in separation. Obtained results suggest that it is feasible to detect microwave energy spatial distribution with the thermoacoustic imaging, which has paved the way to solve the inhomogeneous microwave energy problem in traditional quantitative thermoacoustic tomography.