A spray switch for spray gun includes an elastic wire buckled to a main pipe of the spray gun. The elastic wire has symmetric lateral portions and symmetric guide pins on two ends thereof. A press handle pivoted to a main body of the spray gun is capable of controlling a flow of water. The press handle has an open slot for slidly arranging the spray switch. The spray switch is assembled by a guide block and a buckle unit. The guide block has symmetric guides and recesses on two lateral sides for guiding and holding the guide pins. The spray switch can be switched up and down along the open slot to switch the guide block for engaging or ignoring the guide pins so as to switch the spray gun between modes of auto spray and manual spray.