Drainage device with farmland foreign matter intercepting and automatic cleaning and collecting functions

The drainage device comprises a drainage mechanism and a cleaning mechanism, the drainage mechanism is provided with a power mechanism driven by water flow flowing through the drainage mechanism, and the cleaning mechanism is connected with the power mechanism and driven by the power mechanism to clean the drainage mechanism; the drainage mechanism comprises a filter screen and a body with a water passing opening, and the filter screen covers the water passing opening. The cleaning mechanism comprises a brush, the brush is installed on the body in the mode that the brush moves back and forth to clean the filter screen, and the power mechanism is connected with the brush and drives the brush to move back and forth. The waterwheel flywheel of the power component drives the flywheel through water flow impact to achieve reciprocating motion of the power component, the filter screen can intercept foreign matter in water during drainage, the brush is connected with the power component and reciprocates on the filter