The invention relates to an intelligent fresh and return air volume adjusting type air purifier. The intelligent fresh and return air volume adjusting type air purifier comprises a box, a fresh and return air heat exchanger, an exhaust fan, an air feeder, a controller, a primary filter and an efficient filter. The box is provided with an outdoor exhaust port, an outdoor fresh air port, an indoor air feeding port and an indoor exhaust port. The outdoor fresh air port communicates with the indoor air feeding port through an air inlet channel. The indoor exhaust port communicates with the outdoor exhaust port through an exhaust pipeline. The air inlet channel and an exhaust channel are arranged in a crossed isolation manner, and the fresh and return air heat exchanger is arranged at the intersection position of the air inlet channel and the exhaust channel. According to the signals of indoor and outdoor PM2.5 concentration, indoor CO2 concentration, the air feeding temperature, the fresh air temperature, the indoor and outdoor pressure difference and the like, a controller is used for intelligent comparison and selection, and optimized running of five work conditions of all fresh air, all return air, the minimum fresh air ratio, the minimum return air ratio and fresh and return air mixed adjustment is achieved. The indoor air exchange requirement and the air quality are guaranteed, meanwhile, the dust filtering and containing amount of all levels of filters is reduced, air treatment energy consumption is reduced, and the air feeding comfort degree is guaranteed.