Ecosystem service function is the core of ecosystem evaluation and research hotspot of ecology/environmental economics. Qinling-Bashan Mountains which lies to the upstream of the Hanjiang River is one of the important water supplying and conserving area for China. In recent years, the degradation of forest ecosystem and the capacity of water supplying and conserving in the area have been restricted by both of the natural and human being factors. The dynamic changes of water conservation founction in the Upper Hanjiang River were analyzed by making use of In-VEST model. The results showed that the amount of water conservation of forest ecosystem in the upstream of Hanjiang River was 120.79×10¹⁴ m³ meters, The maximum depth of water conservation was 362.51 millimetres, the average depth of water conservation was 80.69 millimetre. The water conservation evergreen broad-leaved forest was the largest compared with other forest landscape, and the tree garden was the least. From the perspective of space, the amount of water conservation in north and south of Qinlig-Bashan Mountains area was larger, and water conservation function was obvious.