Abstract: Taking River Kaidu Catchment as the research object, 15, 12 and 17 sampling sites were set up in the upstream tributaries, the mainstream of River Kaidu and the downstream Lake Bosten, respectively. Nine water environmental investigations were conducted during June to October in 2014 and June to September in 2015. The spatial-temporal distribution characteristics of physiochemical parameters in different water bodies in River Kaidu Catchment were explored, and the related reasons were discussed. The results showed that the main physiochemical parameters in tributaries, mainstream and Lake Bosten differed significantly along different spatial-temporal scales. pH, water temperature, total dissolved solids (TDS), total nitrogen (TN), permanganate index (COD_Mn) and chlorophyll a (Chla) in tributaries and mainstream were significantly lower than those in Lake Bosten, while the turbidity in tributaries and mainstream was significantly higher than that in Lake Bosten, especially during the rainy season from June to August. The concentration of total phosphorous (TP) in mainstream was significantly higher than that in tributaries and Lake Bosten. The average concentration of TDS in Lake Bosten was 1.62 mg/L, indicating a status of oligosaline of this lake. The spatial distributions of TDS, TP and COD_Mn in Lake Bosten were similar, showing the spatial distribution characteristics of northwest > southeast > southwest. The average concentration of TN in Lake Bosten was 0.88 mg/L, and showed a decreasing trend from the northwest Huangshuigou area and southwest river mouth area to mid-lake as well as the east of the lake. The spatial characteristics of salt and nutrients in Lake Bosten were closely correlated with the frequent agricultural activities in the catchment and the input runoff from River Kaidu.