The invention relates to a stage dynamic separation device for a hypersonic wind tunnel model and an application thereof. The stage dynamic separation device comprises an outer sleeve, a piston rod arranged in the outer sleeve, a cylinder driving device arranged at one end of the piston rod and used for driving the piston rod to reciprocate in an axial direction, and a crank connecting rod mechanism arranged at the other end of the piston rod. The crank connecting rod mechanism comprises two crank connecting rod parts which are oppositely arranged. The crank connecting rod part comprises a crank and a connecting rod connected with each other. one end of the connecting rod is connected to the piston rod, and one end of the crank is connected to the outer sleeve. The cylinder driving devicedrives the crank connecting rod mechanism to expand toward the periphery of the crank connecting rod mechanism or to contract toward the middle of the crank connecting rod mechanism by driving the piston rod to reciprocate in the axial direction. The separation device of the invention has the advantages of high separation speed, high reliability, and high use efficiency, and does not interfere with the process of free movement of the separator stage model in the flow field after separation.