The invention discloses a pesticide sprayer capable of controlling pesticide mixing concentration instantly. The pesticide sprayer comprises a frame, wheels, a water tank, a pesticide container, a mixing container and a sprayer body, wherein the wheels are mounted below the frame, the water tank, the pesticide container and the mixing container are fixedly mounted on the frame, a water injection port is formed in the upper side of the water tank, a water outlet is formed in the side face of the water tank, a liquid outlet is formed in the side face of the pesticide container, and a liquid injection port is formed in the upper side of the pesticide container. One end of a water outlet pipe is connected to the water outlet of the water tank, the other end of the water outlet pipe is connected to the mixing container, one end of a pesticide pipe is connected to the liquid outlet of the pesticide container, and the other end of the pesticide pipe is connected to the mixing container. A control switch is arranged at an outlet of the mixing container, a control handle is arranged on the left of the frame, the control switch is connected with the control handle through a connecting line, the bottom of the outlet of the mixing container is connected with the sprayer body through a water hose, and the sprayer body is fixedly arranged at the right end of the frame. The pesticide sprayer is capable of controlling pesticide mixing concentration effectively and reducing workload of spraying pesticides to improve spraying efficiency.