Fine measurements have been conducted to temperatures and their gradients of six wells of the Jinsha River Groundwater Observational Network. The results show that the influence depths of sun radiation heat are 50m to 125m, average temperature gradients in the wells range from 0.11 to 2. 81℃/hm and most are 1 - 2℃/hm, and the temperature gradients on varied depth sections of one well are highly changeable. Lithology of strata and their integrity, particularly high-angle crashed fault zones, have imposed major effects on the influence depths of sun radiation heat and temperature gradients of the wells. The micro dynamic characteristics of water temperature, such as coseismic effects, tidal effects and anomalies of the wells prior to earthquakes, probably depend, to a large degree, on the temperature gradients of the depths at which the water temperature sensors are settled.