Abstract: Particle velocity is an important parameter describing the flow state of gas-solid two-phase flow.A measurement method of solid particles mean velocity based on the spatial filtering effect of the electrodynamic sensor was developed.The spatial filtering characteristics of the electrodynamic sensor were described quantitatively，from which the relationship between the frequency characteristics of the output signal of the electrodynamic sensor and particle velocity was obtained.The effects of geometry parameters of the sensor，particle velocity distribution，particle concentration distribution in the pipe cross section，particle size，particle type and frequency resolution on the measurement of particles mean velocity were also investigated.Off-line experimental results in a gravity-fed particles flow apparatus were presented.The measurement method was verified by the fundamental theoretical and experimental results.