The invention discloses an operation device used for water conservancy. The operation device comprises a hull. A propeller device is arranged on the hull and comprises a main shaft, a paddle shell, anadjusting sleeve and paddles. The main shaft is rotationally connected to the paddle shell and is in threaded connection with the adjusting sleeve. The adjusting sleeve is located in the paddle shell. Three hinging seats are evenly distributed on the outer side wall of the adjusting sleeve. Each hinging seat is hinged to a connecting rod. The three paddles are evenly distributed on the side wallof the paddle shell. Each paddle is rotationally connected to the side wall of the paddle shell through a rotary disc. A rotary rod is arranged in the eccentric position on the bottom face of each rotary disc. Each rotary rod is rotationally connected with one end of the corresponding connecting rod. A pin is further arranged on the paddle shell. One end of the pin can be inserted in or pulled outof the main shaft, so that the paddle shell and the main shaft synchronously rotate or are released from transmission connection. The operation device is beneficial to removal of weed twined on a propeller.