Determing sampling time interval of tracking data is the basic work of naval gun fire control radar in tracking precision experiment, which chiefly depends on autocorrelation time of radar tracking error character. Sampling time interval has direct influence on test voyages and test efficiency. Based on the basic theory of autocorrelation estimate, methods of calculating autocorrelation time of radar, including covariance function and FFT transform are presented, combined with engineering application, some experimental results are also analyzed, which verify that error data sequence of fire control radar is stationary. The weak correlation time of radar tracking error for typical targets was analyzed, sampling time interval of aerial target according to weak correlation coefficient of range and azimuth angle K was made with 1 to 2 seconds, and 2 to 3 times interval of elevation angle suggestion during data processing was made as well. The autocorrelation analysis results show that radar servo system has cancellation residue towards warship rolling; which has certain guidance in improving radar techniques and analyzing tracking error sources in the future.