The invention specifically relates to a modular unit for wastewater treatment and a wastewater treatment method thereof, belonging to the technical field of water quality purification. The modular unit comprises a conveying component, a filtering water purifier, an online monitoring component and a PLC control component, wherein the filtering water purifier, the online monitoring component and thePLC control component are connected by the conveying component to form a normal operation loop and a filtering water purification module regeneration loop; and the filtering water purifier is internally provided with a separation component composed of a plurality of modules. According to the invention, through functional design and combination of system units, different functional units can be flexibly selected according to process requirements so as to achieve process purposes, so the modular unit has good adaptability.