The invention provides a control method and system of refrigerant charging and an air conditioner. The control method of refrigerant charging comprises the steps that a system pressure parameter is obtained; when the system pressure parameter is smaller than a preset pressure parameter, a refrigerant charging valve is controlled to conduct first stage charging; a temperature change rate of a heatexchanger tube temperature is obtained; and the refrigerant charging valve is controlled to conduct second stage charging according to the temperature change rate of the heat exchanger tube temperature. According to the control method of refrigerant charging, manual judgment and operation are not needed, when the number of refrigerants in a refrigerant tank is low, the refrigerant charging valve can be controlled to conduct first stage charging, namely rapid charging according to the system pressure parameter without the need of starting up an air conditioning system, the rapidness of refrigerant charging is ensured, meanwhile second stage charging, namely precise charging, can be controlled to be started up according to the temperature change rate of the heat exchanger tube temperature, and the precision of refrigerant charging is ensured; and the problems that time is wasted, the accuracy is low, and the system life is prone to being shortened due to manual judgment and operation aresolved.