The invention provides a carbon dioxide subcritical extraction, recycling and reusing method for the electrolyte of a waste lithium ion battery, belonging to the field of recycling and reusing of solid waste. The method comprises the following steps: after complete discharging of the waste lithium ion battery, dismounting the waste lithium ion battery and removing a shell, positive and negative terminals, sealing rings and cover plates; transferring the electrolyte, current collectors with positive and negative electrode materials and a diaphragm into a supercritical extraction apparatus; adjusting the temperature, pressure, extraction time and flow of a supercritical carbon dioxide fluid and extracting an organic solvent and an additive; and subjecting the obtained solvent to component analysis, supplementing electrolyte salt, the organic solvent and the additive according to analysis results and adjusting a ratio to prepare electrolytes with different functions. The method effectively prevents degradation and dissipation of heat-sensitive substances; operation parameters are easy to control; extraction, separation and recovery are integrated together; later complicated treating procedures are omitted; and the utilization rate of resources is higher.