Abstract: In order to achieve high accurate measurement of objects velocity, a laser Doppler velocity radar system is established and the frequency estimation algorithm is investigated. The frequency estimation method based on autocorrelation operation is improved and the best performance of it is obtained. A new frequency estimation synthetic algorithm based on the Quinn and improved autocorrelation algorithms is propounded, which is adaptive to the Signal-Noise Ratio (SNR). Monte Carlo simulation and rotating cylinder experiment are carried out, and the experimental results indicate that the new algorithm is better than the methods previously reported. The root-mean-square error of the system is smaller than 2 mm/s and the relative error is less than 0.06 % while utilizing the new algorithm. The experimental results are consistent with the analytical and simulation results.