Abstract: The determination of geothermal reservoir temperature can provide significant parameters for evaluating geothermal resource potential. Qabqa area of Qinghai Province is enriched in geothermal resources, but it is difficult to determine the deep geothermal reservoir temperature. Based on the two hot water wells in Qabqa area, combined with their hydrochemical characteristics, various methods are used to estimate the deep geothermal reservoir temperature. The results show that the temperature scale of SiO₂ is the most indicative. The correction of mixing of cold water and degassing by PHREEQC software makes the calculation results relatively accurate and reliable. Through mutual verification of several methods, it is finally determined that the Neogene geothermal reservoir temperature in Qabqa area is 86-107℃, with the geothermal gradient about 6℃/100 m.