The application relates to a liquid drinking machine full-automatic liquid injection method and device, and a liquid drinking machine. The liquid drinking machine full-automatic liquid injection method comprises the following steps of: obtaining a cup height sensing signal sent by a height sensing device and a liquid level detection signal sent by a liquid level sensor after receiving a cup detection signal sent by a cup sensor; outputting a liquid discharge instruction to control internal components to perform a liquid discharge operation when it is detected according to the cup height sensing signal and the liquid level detection signal that a preset liquid discharge condition is satisfied; and outputting a stop instruction to control the internal components to stop liquid discharge whenit is detected according to the cup height sensing signal and the liquid level detection signal sent by the liquid level sensor in real time that a preset stop condition is satisfied. According to the invention, the liquid discharge is performed only when the cup in the placement area meets the requirement; and the liquid discharge is stopped when it is detected that the preset stop condition issatisfied during the liquid discharge process of the liquid drinking machine; therefore, the automatic liquid injection and the stopping of liquid injection of the liquid drinking machine are realized, no manual operation by the user is required, and the convenience of use is improved.