Laozishan is a typical geothermal field in Subei Basin. The authors conducted a systematic study to explore into the genesis mechanism. The results show that the genesis model of the geothermal field postulated to be a low-medium temperature geothermal system of convective type. The recharge area is located in the Zhangbaling to the Xuyi mountain chain with a distance of about 60 km to the south of the geothermal field.  The thermal water flows upward in Laozishan area in the intersection zones of the faults striking NNE-SSW and NW-SE.