Aims Alpine meadow is widely distributed in the Qinghai-Xizang Plateau,playing an important role in regulating the regional carbon budget.Over the Qinghai-Xizang Plateau,precipitation generally shows an increasing trend during past the several decades,and is projected to increase during the 21st century.Alpine meadow is very susceptible to such climate change,but it remains unclear how its ecosystem carbon exchange responses to precipitation change.In this study,we aim to clarify the effects of altered precipitation on ecosystem carbon exchange in the alpine meadow by conducting a manipulative field experiment.Methods We conducted a precipitation manipulation experiment at an alpine meadow site in the Namtso area of central Qinghai-Xizang Plateau during 2013 to 2014.A total of six treatments were established,with levels of water addition set for 0%,20%,40%,60%,80% and 100%,respectively,of equivalent increases in precipitation.We investigated the effects of water addition on gross ecosystem production (GEP),ecosystem respiration (ER),net ecosystem carbon exchange (NEE),and environmental conditions during the growing season.Important findings The increasing water addition substantially increased soil moisture,but had no significant effect on soil temperature.Both GEP and NEE significantly increased with water addition equivalent to 20% of increases in precipitation,but were suppressed with further increases in the level of water addition.No significant difference was detected in ER across the water addition treatments.Our study suggests that:1) The change in soil moisture significantly affected NEE and GEP but had a weak effect on ER in the alpine meadow;2) CO_2 sequestration in the alpine meadow could be stimulated by moderate increases (e.g.20%-40%) in precipitation.