The invention discloses a bypass type passive pneumatic vectoring spraying pipe provided with a sliding-type switch and a design method for the sliding-type switch. The bypass type passive pneumatic vectoring spraying pipe comprises a bypass channel formed in an inner flow channel of a spraying pipe body; the sliding-type switch is mounted at the outlet position of the bypass channel; and the sliding-type switch comprises a sliding groove and a sliding sheet, wherein the inner profile surfaces of the sliding groove and the sliding sheet are both in an arc shape. Through moving of the sliding sheet, the sliding-type switch achieves opening/closing of the bypass channel; when the bypass channel is opened, the sliding sheet can be embedded into the sliding groove; when the sliding sheet closes the bypass channel, one end of the sliding sheet is connected with the sliding groove, and the other end of the sliding sheet is tangent to the end, where an outlet position point A is located, of the bypass channel; and meanwhile the outer profile surface of the sliding sheet protrudes out of the outlet section of the bypass channel. Therefore, according to the switch, through the specially-designed outer profile surface protruding out of the outlet section of the bypass channel, a throat channel downstream flow field flow structure is changed, original oblique shock waves are changed into lambda-shaped shock waves, flowing is closer to the wall surface, the vectoring performance is more excellent, and the flow loss is quite small.