With the aim of making local particle flow structure studies in commercial scale circulating fluidized-bed (CFB) boilers, a momentum probe and a non-isokinetic particle sampling probe have been designed to measure local momentum flux of gas-solids flow and particle flux. The time-averaged, local particle velocity and concentration are deduced from the measurement results of these two probes. The two probes were calibrated and validated in situ in a CFB boiler furnace. In order to better understand the principle of the momentum probe and to ensure reliable measurements, a theoretical model is established by focusing on the particle deceleration movement inside the probe tip. This model is able to predict the relationship between the gas-solids momentum flux and the impact pressure as obtained from the calibration.