Writers measured the spring temperature and rate of flow in Julongquan sprin gs of Tianchi Lake, Changbai Mountains. In the field works, some water samples and 6 rock samples are collected. The regular composition of the water samples is ana lysied, and the heat conductivity of rock samples is measured. The springs thermal wate r compositions of K+、Na+、Ca2+、Mg2+、SO2-4、 HCO-3、SiO2 are given out. There are four groups parameters of water samples that be selected to calculate thermal reservoir tem peratures and depth of Julongquan springs in Changbai Mountains. The SiO2 temp erature m eter is used in calculating thermal reservoir temperatures. According to Donaldsons thermal water circulating pipe model and with nondimensiona l temperature parameters, and according to Rybach's one group curves of nondimensional tempera ture circulating depth, we estimate the thermal water circulating depth. With t he depth, the temperatures of thermal water reservoir and surface and the conduc tivity of rock samples, the temperature gradient and heat flow are estimated in Julongquan area of Tianchi Lake, Changbai Mountains.