A processing unit, method, and device for vehicle air conditioner warning are disclosed. The processing unit is configured to judge a ventilation state of the current vehicle location based on positioning satellite signals, to judge an operation state of the vehicle engine based on information, to judge a running state of the vehicle based on information received, to judge a using state of the air conditioner based on information, to judge a vehicle door/window opening/closing state based on information, and to determine that there is a potential risk of poisoning and initiate the warning element when all the following conditions are met: the ventilation state at the current vehicle location is bad, the engine is in operation, the vehicle is in a stopped state or runs at a low speed, the air conditioner is being used, and all the doors and windows of the vehicle are closed.