The violent inertial cavitation effect generated during high intensity focused ultrasound (HIFU) treatment may damage healthy tissues around the target area. Therefore, it is urgent to develop new technical approaches that can quantitatively monitor the acoustic cavitation motions in biological tissues with high precision in space and time, so as to ensure clinical safety and effectiveness. Compared with the traditional commercial ultrasonic gray value signal, the ultrasonic radio frequency (RF) signal can better retain more detailed information of the acoustic scattering signal. As a statistical parameter not based on mathematical function model, information entropy can characterize the spatiotemporal evolution state of disorder of scatters inside tissues resulted from acoustic cavitation. Therefore, this paper proposed a real-time monitoring system for spatiotemporal evolution of acoustic cavitation based on the entropy analysis of ultrasonic RF signals. First, the original RF signal of scattered echoes generated by HIFU-induced cavitation bubbles inside the gel phantom was obtained using a modified B-ultrasound system, and the two-dimensional mean filtering method was used to suppress HIFU-induce strong interferences overlapping with cavitation monitoring imaging signals. Then, the dynamic variation range of the RF signal was expanded through data standardization processing, and the entropy image was reconstructed based on the sliding window information entropy analysis to demonstrate the spatiotemporal evolution status of HIFU-induced cavitation behanviors. The experimental results indicated that the acoustic cavitation imaging algorithm based on RF signal entropy analysis should be more sensitively and accurately than B-model gray scale imaging method for determining the onset time and spatial position of cavitation activities, which was helpful for ensuring the safety and efficacy of HIFU clinical treatment. The current work would provide a useful tool for the spatiotemporal monitoring of the acoustic cavitation generated in tissues during HIFU treatment, and lays a solid theoretical and experimental foundation to establish an effective quantity-effect evaluation system for the cavitation related biological effect.