Abstract: By dimensional analysis,the author comes to the conclusion that the movment of flyer plate in explosive welding is on geometric analogy.However,due to the rarefaction effect from the initiating end,there is an unsteady range in addition to the steady range of the movement.In the steady range,the maximum dynamic bent angleof flyer plate depends only on one dimensionless parameter R,whilst in the unsteady range the Iimiting dynamic bent angle depends on two dimensionless parameters,R and (he)/(V_Dt)(ratio of explosive thickness to distance of detonation wave front from initiating end).The above conclusion has been verified by experiment.A value of (he)/(V_Dt)=0.04 as the threshold is given.