Radar velocity meters are widely used in hydrological survey. At present, there are some problems from the products, such as lowvelocity accuracy, influence of wave or other external environment, insensitivity at low velocity and etc. The Maximum Interpolation Fitting (MIF)based on Fast Fourier Transform (FFT) has been adopted for accuracy enhancement of flow velocity computing. Besides, the frequency conversionwas introduced for the accuracy of low velocity measurements. These research results were applied to a new-type radar current meter, and the testsof simulation and verification were carried out also. Field site tests indicate that the methods are reasonable and feasible, which can solve the aboveproblems commonly existing in radar currentmeters.