A modified impact probe for continuous measurement of solids circulation rate in a circulating fluidized bed has been developed based on a principle similar to a momentum probe. The response curves of solid flow from the probe have been characterized and calibrated in a test column (0.05 m-I.D.×0.80 m-high). The probe was validated in situ in the downcomer of a circulating fluidized bed (0.10 m-I.D.×4.80 m-high). The solid circulation rates obtained by the modified impact probe well agree with the measured solids circulation rate by the descent time method.