Position limiting improved switching valve

A switching valve with an improved positive stop structure is disclosed which includes a structure of a valve body, a valve button, and a bottom ring margin. The utility model is characterized in that: the valve button bottom ring margin of the switching valve is provided with a truncated ring margin which can be in a close ring connection with the valve body surface. A lug boss is arranged at a proper position, which is in a certain distance from the bottom ring margin, in the inside of the valve button. The lug boss is right arranged in the eccentric path which the valve button rotates along. Thus, the valve top surface is provided with a positive stop block which corresponds with the lug boss. The two end positions of the positive stop block can be rotated clockwise or anticlockwise through the valve button to a preset static angle and resist the lug boss for positive stop.