In order to reveal the trend of water chemistry change in the Yarlung Tsangpo River (Yajiang River) under the background of climate change and provide scientific and technological support for water resources and water environment management in the basin, based on the study of hydrochemical characteristics of the Yajiang River in 2016, 2017 and 2018, combined with the research results of existing research teams on hydrochemistry, this paper studies the trend of 11 hydrochemical components change of the upper, middle and lower reaches of the Yajiang River over the past 60 years by comprehensive use of linear tendency estimation, climate change model output and BP neural network model. The results show that the annual average temperature in the upper, middle and lower reaches of the Yajiang River Basin has been increasing obviously in the past 60 years. The average temperature warming rate was 0.38°C/10a. The precipitation in the Yajiang River Basin fluctuated obviously and showed an overall rising trend, with a rising rate of 7.34 mm/10a. pH value of the water in Yajiang River was weakly alkaline and showd an upward trend. TDS was higher than the average level of the world river (120 mg/L) and showed a trend of gradual increase. Based on the climate change model RCP4.5 scenario, the artificial neural network prediction shows that the TDS flux in the upper, middle and lower reaches of the Yajiang River Basin presents a gradually increasing trend, and the downstream will have a certain impact on the production and life of the downstream residents.