Agricultural knapsack sprayer

The utility model discloses an agricultural knapsack sprayer which is composed of a tripping lever, a liquid storing box (1), a pump (2), a pressure-stabilizing can (3) and a spray tube (4). The pump is composed of a pump body (9), a piston body (6), an O-shaped sealing ring (7) which is inlaid in the piston body, a piston rod (10), a leakage stopping plug (8), an upper cover (5), etc. The sealing ring (7) and the inner wall of the pump body has good abutting performance, so that the utility model has stable wear resistant and airtight performances; a guiding hole on the leakage stopping plug (8) is closely matched with the piston rod, so that the utility model has good leakage preventing function. The utility model solves the problems of easy air leakage for a piston and easy liquid leakage at the side of a piston rod existing in common sprayers. The improved parts have simple structure and easy manufacture, and the utility model can also be used as a subassembly for improving the working performance of old style sprayers.