The existing D8PSK demodulation methods suffer from long frequency offset estimation time and complex algorithms. To address these issues, this paper proposes a correlation demodulation-based direct phase compensation method. By optimizing the synchronization timing acquisition and deviation correction algorithms, the demodulation accuracy of D8PSK signals in VDB systems is enhanced. FPGA hardware platform testing demonstrates that this method satisfies the bit error rate requirements of VDB receivers under large dynamic range variations.