The utility model relates to a composite tower plate used in a mass transfer separation device, and more especially, a float valve and screen hole composite tower plate is designed, wherein circular screen holes and float valves are arranged on the tower plate; the gradient of the liquid level from an inlet to an outlet of the tower plate can be reduced by the special arrangement of the float valves; no liquid stagnation region and uniform gas distribution promote the gas-liquid mass transfer on the tower plate, and the efficiency of the tower plates is high. The combination of the float valves and the screen holes can increase the operation load range of the tower plates and the treatment capability is large. The manufacture cost of the tower plates is low, and is between the cost of a screen plate tower and the cost of a float valve tower.