The invention discloses a method, a device and a system for remotely controlling an air conditioner. The method comprises the following steps of: after starting the air conditioner of a vehicle, acquiring the detected environmental parameters of the vehicle in the inner space, wherein the environmental parameters comprise temperature and humidity; and adjusting the output parameters of the air conditioner under the circumstance that any one or more environmental parameters in the inner space of the vehicle do not satisfy a predetermined condition. The method, device and system disclosed by the invention solve the technical problem that the environmental quality in the vehicle cannot be guaranteed as the air conditioner of the vehicle cannot be remotely controlled before driving.