Abstract: The Yinchuan Basin is an arid and semi-arid interior basin in northwest China, where a large amount of Yellow River water is used for irrigation. The study on the participation degree and depth of water seepage from irrigation to Groundwater circulation is a key to further solve the water environment problems. Based on the analysis isotopic characteristics of stable and tritium, the distribution relation of isotopic characteristics of different water bodies in Yinchuan basin has been constructed. It is shown that, the mean hydrogen and oxygen stable isotopes of precipitation and yellow river water are all distributed on the GMWL, indicating the characteristic of atmospheric sources. The stable isotopes of deep groundwater, shallow groundwater and drainage ditch water are distributed on the groundwater line (δD=8.24δ¹⁸O+1.08). This groundwater line is approximately parallel to the GMWL. The difference between these two lines points to two dominant processes of water cycles, the evaporation-mixing process and water-rock interaction-mixing process. These two processes indicate to two proportions of irrigation water in groundwater discharge, 44.07% and 89.76% respectively, which point out that water-rock interaction-mixing process is the dominant process.