Abstract: To solve the problem of one-to-one correspondence relationship not existing between state variable and cumulative phase in two-state trellis of shaped-offset quadrature phase-shift keying(SOQPSK-TG), a decision feedback demodulation algorithm for recursive SOQPSK-TG is researched. According to a two-state trellis , cumulative phase corresponding to the state variable is obtained by decision feedback in state transition. Simulation results show that at Eb/N0≥0 dB, the decision feedback demodulation algorithm can achieve a BER performance which is very close to four-state demodulation algorithm performance.