Abstract: A control valve assembly for spray guns comprises a flexible valve having a water-sealing portion defined by a support surface and an abutment surface conjoined to a pivoting rod via a water-stop surface disposed there-between. A water-pressure adjusting valve includes a pressure-relief section having a flow orifice to mount to a valve shaft of a pressure valve and match to the pivoting rod and the abutment surface of the flexible valve thereby. The pressure-relief section, precisely situated between a stop seat of a spray gun body and a valve seat, has a watertight ring fixed at one side to closely abut against the stop seat. A support section, extending at the other side of the water-pressure adjusting valve, has a pivoting hole defining the end portion opposite to the flow orifice thereof. Besides, the pressure valve has a positioning ring mounted to the predetermined position of the valve shaft thereon.