The daily discharge at the Meigang Station of the Xinjiang River from 1953 to 2010 was selected and divided into two stages namely the original watershed (1953-2001) and the drainage with human impact (2002-2010), based on the running time of the Jiepai Reservoir. The range of variability approach (RVA) which was proposed by Richer was used to study hydrological situation change. Then, the mean value and the difference values of RVA targets were used for estimating monthly ecological flow and transferable water at the Meigang station of the Xinjiang River. The results of ranked median degrees of 33 hydrologic alteration indicators indicate that about 22 indicators had highest or higher change and 11 indicators changed a little. The impacts of the Jiepai Reservoir on the hydrologic alteration is relatively significant with a mean hydrologic alterations (HA) value of 0.51. The values of ecological flow at the Meigang Station are within the RVA threshold that can basically maintain steady river flow to safeguarding river ecological security. However, the values of ecological flow on five months including Feb., Jul., Aug., Sep. and Dec. exceeded the lower limit of RVA value. Measures should be implemented such as increasing the amount of water discharged from reservoir in order to reduce the threat to downstream river ecosystems.