The embodiment of the utility model discloses a multifunctional aeration tank for a modular water treatment device, comprising a reaction tank which comprises a tank body, a movable bracket, a fixed buckle, a water inlet pipe quick connecting and fixing joint, a water outlet pipe quick connecting and fixing joint, an air inlet pipe quick connecting and fixing joint and an emptying pipe, the aeration device comprises an air diffusion device, the air diffusion device is arranged at the bottom of the reaction cavity and connected with the air inlet pipe quick connection fixing joint, and the fixing joint is connected with an air outlet pipe of an external air blower; the functional assembly comprises a biological filler assembly, a membrane bioreactor assembly and a stirring assembly. According to the multifunctional aeration tank for the modular water treatment device, a modular design thought is adopted, all the functional components are connected with the reaction tank through the buckles, different functional components are installed according to different experimental requirements, and one set of equipment can simulate various different water treatment processes.