The invention discloses a multi-frequency ultrasonic washing effect experimental platform which comprises a core control module, a first relay module, a second relay module, a third relay module, an input isolation module, a power amplifying module, a first matching transformer, a second matching transformer, five ultrasonic signal generating modules, five matching inductors and five transducer arrays. A signal output end of the core control module is connected with control signal input ends of the ultrasonic signal generating modules, the first relay module, the second relay module and the third relay module and is used for generating corresponding switching control signals according to input working frequency selective signals and transmitting the signals to the first relay module, the second relay module and the third relay module. Output ends of the five ultrasonic signal generating modules are in selective connection with the input isolation module through the first relay module respectively. According to the multi-frequency ultrasonic washing effect experimental platform, multiple frequency groups can be used for underwater construction object dirt washing effect researching, the effectiveness and the relative property of washing effect are obvious, and the best frequency suitable for underwater construction object dirt washing is found in real time.