Bidirectional ring-coupled Duffing oscillator hasbeen investigated. A phenomenon is discovered, showing that when one of the oscillators is driven by pulsed signal under certain parameter conditions, this and the other oscillators will suddenly change from synchronization to transient non-synchronization and then rapidly return to synchronization, which is defined as transient synchronization mutation in this paper. This phenomenon is used to accurately detect partial discharge signal in strong noise environments. The experimental tests show that this method achieves good detection effect in low SNR for partial discharge signal of different discharge electrode, which can further extend the weak signal detection range based on Duffing oscillator.