Abstract: The ash circulating rate of high-temperature bed material is a crucial parameter for circulating fluidized bed( CFB) boilers,while there is no measurement technology that can be applied to the industrial boiler at present. Therefore,an in-situ impact measurement method for solid particle circulation rate of CFB boilers was proposed in this paper,and its prototype equipment was built. The theoretical model of the measurement process was established and the cold state test was carried out in the laboratory. The proposed measurement method of circulating flow rate measurement was also applied to a 116 MWthCFB boiler for a hot state test. The prototype equipment had the geometry structure of cantilever,which was arranged at the bottom of standpipe in circulating fluidized bed. One end of the prototype was fixed with the outer wall surface of the boiler and the other end carrying a target piece was inserted into the dense phase area of standpipe. The device calculated the impact force of particles and reversed the impact velocity of particles by measuring the deformation caused by the impact on the target plate when the materials in the riser fell,so as to obtain the circulating flow rate. Meanwhile,instrument air is supplied to cool equipment and prevents it from blocking. This measurement method has the advantages of high-temperature resistance,the ability of in-situ measurements and no disturbances to the boiler operation. The results indicate that the resistance and resistance coefficient of gas-solid flow at different impacting velocity are measured in cold state experiment. As the increase of impact velocity,the gas-solid flow resistance increases and the resistance coefficient decreases and the phenomenon of shear shinning appears. In hot state test in real boiler,the measuring method is capable of capturing the variation of the ash circulating rate when the boiler starts,shuts-down and the load changes. Based on the magnitude analysis and the checking calculation with the product of pressure drop of dilute phase area in furnace and average velocity in furnace,the feasibility of the in-situ utilization of the proposed method in CFB boilers is verified.