The invention discloses a device for realizing single-liquid automatic grouting and guniting and a method. The device includes a power output device, a continuously variable transmission, a stepping motor, a shaft speed detector, a pump body, a slurry tank, a grouting pipe and a control system. An output shaft of the power output device is connected to an input shaft of the continuously variable transmission through a coupling, and the shaft speed detector is mounted on an output shaft of the continuously variable transmission to form a differential speed output system. A handwheel, which is used for controlling a transmission ratio, of the continuously variable transmission is connected to the stepping motor, and the stepping motor rotates a specific angle to control the transmission ratio of the continuously variable transmission, thereby automatically controlling rotating speed of a control pump. The output shaft of the continuously variable transmission is connected to a pump bodyto form a pumping system. A suction pipeline of the pump body is connected to the slurry tank, an output pipeline of the pump body is connected to the grouting pipe through a flowmeter, and a pressuresensor is also arranged on the grouting pipe so as to form a slurry mixing and grouting system. The stepping motor, the shaft speed detector, the flowmeter and the pressure sensor are all connected to the control system.