The realtime measurement of the relative parameters of the gassolid twophase flow has great significance for the process control and efficient operation.For the deficiencies of existing parameters measurement method of gassolid twophase flow,a set of acoustic emission signal detecting device with airglass bead has been designed,tested and evaluated according to the classic acoustic emission theory.The different sizes of glass beads have been chosen for acquisition of acoustic emission (AE) signals of velocity and particle sizes in gassolid twophase flow under the impact velocity of 1.98 m/s, 2.80 m/s,3.40 m/s and 4.00 m/s respectively, and analyzed by the power spectrum estimation. The result shows that there are good linear relationship between the magnitude and the area of the power spectrum estimation with the impact velocity,particle sizes. The verifying experiment results show that the relative error of particle size measurement is less than 8.5%.Therefore, the combination of AE and power spectrum estimation is feasible and effective for measuring the particle size of the solid phase.