To solve the problem of frame angular velocity extracting in a semi-strapdown stabilized platform, a velocity measurement scheme is proposed based on nonlinear tracking differentiator, which can avoid the error amplification caused by conventional differential velocity measurement, and can solve the problem of phase delay caused by nonlinear tracking differentiator by using a predictive compensation method.The digital simulation and experimental results show that the nonlinear tracking differentiator can accurately extract the angular velocity signals from the frame angular position signals.The experimental results show that the semi-strapdown stabilized method based on the nonlinear tracking differentiator can isolate the low-frequency angular disturbances as well as the direct stability method does, which proves the feasibility and effectiveness of application of the nonlinear tracking differentiator in the semi-strapdown stabilized platform.