Synchronous and asynchronous vibrations of their flames can be observed with two identical burningcandles at a proper distanceIn order to explore the cause of candle flame vibration,a reflective schlieren lightpath was built to realize the visual observation of candle flame airflow field.With the approach of two candles.the airflow field above the double candle flame will transition from the uncoupled advection state to the coupledturbulent state ,and the downward diffusion of the turbulent region to the flame region is the reason for theflame vibration.The asymmetric fluctuation of flame volume during combustion leads to the switching betweensynchronous and asynchronous oscillation of oscillating flame; During the combustion process , the stability otthe air flow around the flame will lead to the decoupling of the two oscillating flames ,the turbulent layer willrise and leave the flame ,and the flame will resume stable combustion.