Abstract: Based on a 3 D thermal-hydrologic numerical model considering fluid losses for enhanced geothermal systems（EGS）,heat extraction rate is defined as a function independent of injection temperature,and the CO₂-EGS（EGS with CO₂as the working fluid）and the H₂O-EGS（EGS with water as the working fluid）are compared for different injection temperatures. The results show that higher injection temperature restrains heat extraction and CO₂losses（i.e. CO₂sequestration）for the CO₂-EGS,and that higher injection temperature enhances heat extraction but leads to more water losses for the H₂O-EGS. When heat extraction rate is defined by most researchers as a function dependent of injection temperature,the influence of injection temperature on heat extraction performance would be overestimated and underestimated for the CO₂-EGS and the H₂O-EGS,respectively.