The invention discloses a method for carrying out detection and control on ultrasonic intensity in water treatment. The method is characterized in that the output of a power amplifier in water treatment is monitored by using a system for carrying out detection and control on ultrasonic intensity in water treatment, if a detected acoustic intensity is deviated from a reference acoustic intensity, the system automatically adjusts the output power of the power amplifier, so that the value of the acoustic intensity of an ultrasonic water treatment system always remains at a preset reference value, thereby providing an automatic acoustic-intensity stabilization system for researches on ultrasonic water treatment, and ensuring the service life of an ultrasonic transducer; meanwhile, through carrying out measurement of acoustic intensity parameters, an effect that the ultrasonic transducer with different operating frequencies can carry out water treatment under the condition of a same acoustic intensity parameter, therefore, the method disclosed by the invention can be used for solving the problem that in the existing water treatment technology, factors affecting the operation of degradation can not be researched because of the lack of important parameters.