The invention relates to a frequency conversion energy-saving temperature control device of a refrigerating device, comprising a frequency conversion compressor, a condenser, an expansion device and an evaporator; the frequency conversion energy-saving temperature control device is also provided with a first bypass circuit and a flow rate control valve thereof which are used for receiving high temperature and high pressure gaseous refrigerant output by the frequency conversion compressor and outputting the gaseous refrigerant into an input end of the evaporator, as well as a second bypass circuit and a flow rate control valve thereof which are used for receiving high temperature and high pressure gaseous refrigerant output by the frequency conversion compressor and outputting the gaseous refrigerant into an input end of the frequency conversion compressor. By using the hot gas bypass circuits, the first flow rate control valve and the second control valve to respectively reflect volume control, rapid reaction and the temperature change of working fluid of a working machine connected with the evaporator, the device can accurately carry out constant temperature control.