The invention relates to the technical field of hydraulic engineering, in particular to a water gate water level detection device. The water gate water level detection device comprises an elevated stage, a second electric telescopic rod is fixed to the upper surface of the elevated stage, a second output shaft is in slide connection with the upper end of the second electric telescopic rod, and a motor is fixed to the inner side wall of a motor cover which is welded to one end, away from the second electric telescopic rod, of the second output shaft. The motor is in rotational connection with abase through an output shaft. In water gate water level detection, the second output shaft slides to a highest position, then the motor is connected with an external power source, the motor output shaft drives a first electric telescopic rod, a water gauge and the like to rotate centering on the motor, then the first electric telescopic rod retracts or stretches, a water level value of a specified position can be measured, measuring around a certain position and averaging can be realized, and accordingly accuracy in water level detection can be improved.