In high-speed mobile communication systems, there exist two prominent issues-large Doppler spread and limited pilot resource between the transmitter and receiver, which has great influence on the performance of a traditional joint frequency-phase offset estimation. In this case, this paper proposes a parallel processing-based joint frequency-phase offset estimation. First, we utilize a variable delay-length auto-correlation operator to design a frequency-phase decoupling algorithm and apply it to the traditional joint frequency-phase offset estimation. Theoretical analysis and simulation results show that the proposed frequency-phase decoupling algorithm can decouple the phase offset estimation and frequency offset estimation, and can also reduce complexity of the phase offset estimation.