The accurate synchronization is a key technique for the receiver to despread correctly. A new algorithm based on software radio is proposed to track the carrier frequency offset fast. Its realization steps and estimation performance are also discussed. This algorithm gains three advantages: (1) The influence of carrier frequency's initial phase is dismissed. (2) It can be used in signals with very low signal-to-noise ratio. (3) It is easy to implement because of its simple structure. The results of the simulation and test show the feasibility of the algorithm.