Considering phase ambiguity problem of the pilot-symbol-assisted-modulated ( PSAM) based frequency offset estimation , this paper proposes a novel time-domain frequency offset estimation algorithm. First, a partial cross correlation ( PCC) algorithm is derived with the use of the idea of the autocorrelation algorithm , capable of eliminating complex multiplication operation. Then , a phase- unwrapping algorithm is proposed based on Monte-Carlo simulations, and by using it an improved PCC ( IPCC) algorithm is also derived , which is adaptive to larger frequency offsets. Finally, simulation results show that comparing with the existing classical algorithms(i.e. , theM&Mand ACalgorithms), the proposed IPCCalgorithm exhibits the highest accuracy while theM&Mis the worst； and the IPCCalgorithm has linearly computational complexity but the AChas the highest computational complexity.