Abstract: To explore the effects of saline water on cotton under mulch drip irrigation in Xinjiang, the authors used the mixing of saline water from alkali discharge canal with river water, set river water as the control (CK) and two treatments of saline water salinities of 3 g/L and 5 g/L, to study the effects of saline water drip irrigation on cotton canopy photosynthetic characteristics and cotton yield and quality. The results showed that the effects of saline water irrigation on cotton at early flowering stage was not obvious, and gradually increased to the full-blossom stage; compared with the control, saline water drip irrigation decreased cotton LAI, MTA and Pn, and the decreasing effect of 5 g/L treatment was more than that of 3 g/L treatment, but the transpiration rate and stomatal conductance of 3 g/L treatment was higher than that of CK and 5 g/L. Saline water drip irrigation decreased cotton yield, 3 g/L treatment had less obvious effect than 5 g/L treatment, the main reason was the number of bolls per plant decreased significantly, while boll weight increased, and lint percentage had no obvious change. Saline water had no significant effect on the fiber length and specific strength, but the Micronaire value increased significantly. Therefore, low saline water can be used in cotton production in Xinjiang to alleviate the drought and achieve high and stable yield.