Blood perfusion depends on blood flow and vessel in local tissue, which plays important role during hyperthermia. Laser speckle imaging technique was developed to obtain the regional blood flow distribution with high spatio-temporal resolution. Through LSI method, the velocity and diameter change of microvessels can be acquired simultaneously. In this paper, the spatiotemporal characteristics of local mesentery blood flow in anesthetized rats during thermal therapy (43°C, 45°C, 47°C, 49°C, 60min) were monitored in vivo and real time by laser speckle imaging method. The blood flow distribution image of microvessels diameters in 10-50μm was obtained and analyzed to get the information of the response of the diameter of blood vessel, the velocity of blood flood and the perfusion to hyperthermia. The results showed that the diameter of microvessels increased firstly, then decrease appeared if heated continuously while heated at 43°C, 45°C. The same trend could be found for changes in blood velocity and blood perfusion. While heated at a higher temperature, for example, at 47°C, 49°C, the diameter and blood velocity of microvessels decreased soon. This indicated that the microvessels underwent thermal damage. The thermal damage exhibitions were obvious when heated at higher temperature, and the blood flow blanking even may appear. In general, the blood flow of branch stops early more than the blood flow on the backbone. The analysis of the damage rate showed that the higher the heating temperature, the quicker the damage rate.