The ring coupled Duffing oscillator was investigated, a phenomenon was observed when analyzing the synchronization evolution between coupled oscillators, which shows that if all oscillators are driven by the same periodic driving force,the motion trajectory between weakly coupled oscillators will generate two abrupt changes from synchronization to non-synchronization and then to synchronization in the phase transition of period-doubling bifurcation, chaotic state and large-scale periodic state. Any synchronous abrupt change can be used to rapidly identify system phase transition, and thus a weak periodic signal detection method was proposed based on the phase transition of period-doubling bifurcation and chaotic state.