The invention discloses a device and method for injecting a phase change material into a plastic hose. The device comprise a storage tank, an air compressor, a compressed air pipeline, a fluid conveying pipeline and a temperature control heating device. According to the device and the method, the temperature of the injected phase change material is adjusted through the temperature control heatingdevice, the pressure in the storage tank is increased by utilizing the air compressor so that the phase change material can be injected into the plastic hose; through a constant temperature control method, the viscosity of the phase change material in the injecting process can be ensured not to be increased, the injecting speed can be increased, the injecting time is shortened, the injecting pressure can be controlled conveniently, the device and the method can adapt to the working pressure of the different plastic hoses, the defects that manual injecting is low in efficiency and is limited ininjecting length are overcome, meanwhile, the problems that during injecting by an existing mortar pump or other mechanical pumps, the internal structure is complex and inconvenient to maintain, thephase change material is prone to corroding a pump body, and the injecting pressure and the injecting amount are difficult to control are solved; and equipment investment and operation cost is low, the operation is simple, injecting can be carried out on the plastic hoses with different sizes, different pressure and different heat resistance, and the adjusting range is wide.