A multifunctional air conditioner mainly comprises a case, an inner fan, an outdoor unit, an exhaust fan, a fresh air valve, an air exhausting valve, an evaporator, an air purifying valve, an inner side valve, an ultraviolet lamp and/or negative ion, a controller, a displayer, heat exchangers, a purifying assembly, an indoor temperature and humidity sensor, an outdoor temperature and humidity sensor, an indoor gas sensor, an outdoor gas sensor, a connecting pipeline and a by-pass valve. The controller controls the inner fan, the outdoor unit, the exhaust fan and all the air valves so that the multiple functions of the air conditioner, a fresh air machine, the air purifier and the like can be achieved, and the requirements of people for the temperature, freshness and purity of the air are fully met.