A set of realtime microwave thermoacoustic imaging system was established. The system was composed of a pulsed microwave generator, a multielement ringshaped detector, a multichannel data acquisition and a data reconstruction device. From experiments, the performance of the two plastic tubes filled with physiological saline was verified, and the results showed that the imaging speed was 16.7 frames per second. Subsequently, the normal and tumor area of the living mice were imaged, respectively, and the contrast between the tumor and normal area was 1.7〖DK1〗∶1, which proved that the system had a high contrast in tumor detection. Finally, a dynamic process monitoring experiment was implemented. In summary, the established system has the advantage of noninvasive, fast imaging speed and large field of view, and is expected to be widely used in biomedicine, especially realtime tumor screening and monitoring. 