The frequency tracker of doppler radar is analyzed here, which would be applied to the velocity computation of an aircraft for self-contained navigation. The radar signal is assumed to be the stationary Gaussian noise having the spectrum spread about 1/10 of the doppler frequency (I. e. the center frequency of doppler signal). The frequency tracking is performed by the servomechanism composed mainly of the synchronous detection (S-D) type of frequency discriminator and the voltage controlled oscillator. Experimental results are also given showing good coincidence with the theoretical analysis.