The invention discloses a temperature adjusting system for electric vehicle batteries, comprising: a first reel and a second reel arranged on two sides of a battery box respectively, wherein the firstreel is rotationally arranged in an insulation barrel; a first motor and a second motor; a belt that includes two layers of base cloth sewn together and a heat-absorbing portion including a pluralityof heat storage tubes sewn between the two layers of base cloth, wherein the heat storage tubes are filled with a phase change material; an environmental temperature sensor; a battery temperature sensor; a heat storage tube sensor; a controller that captures an electric vehicle stop signal from an electronic control unit, wherein the heat-absorbing portion covers the lower portion of the batterybox for a period of time when the environmental temperature is lower than the lower limit of environmental temperature, and a hollowed-out portion is reeled to the second reel; wherein the controlleracquires an electric vehicle start signal from the electronic control unit, and the heat-absorbing portion covers the lower portion of the battery box when the battery temperature is lower than a lower limit of battery temperature. The temperature adjusting system for electric vehicle batteries provides automatic adjustment for battery temperature efficiently and helps extend the service life of each battery.