Aiming to explore the mild salinization area ratio of different water and nitrogen physiological characteristics, yield and quality of drip-irrigated cotton, the influence of irrigation water use efficiency and nitrogen partial productivity, seek water and nitrogen combination suitable for cotton cultivation in salinization area, and optimize the salinization area for drip irrigation cotton basis, barrels and randomized trials were used, three irrigation levels of 2750m3/hm2, 3750m3/hm2 and 4750m3/hm2 (W1, W2 and W3) and three nitrogen levels of 300kg/hm2, 600kg/hm2 and 900kg/hm2 (N1, N2, and N3, form of nitrogen in urea) were set up in mild saline soil, and the photosynthesis, fluorescence, yield and quality of cotton, water and nitrogen use efficiency and optimal irrigation fertilization mode were investigated. The results showed that mild salt stress under the condition of different water and nitrogen regulations, irrigation water and the interaction of water and nitrogen had significant effects (P<0.01) on Pn,Tr and Gs and Ci in the growth period, under the level of W1 and W2, Pn, Tr and Gs were increased with the increase of N application rate and then decreased, and reached the maximum at W2N2 treatment. At the level of W3, it was increased with the increase of N, while Ci showed the opposite trend. The influence of irrigation water on Fv/Fm and Fv/F0 of different growth stages of cotton was not significant (P>0.05), and it had significant influence on qp and NPQ, Y(Ⅱ) and ETR (P<0.05). The effect of nitrogen application on NPQ in the growth stage of cotton was not significant (P>0.05), and it had significant influence on Fv/Fm and Fv/F0, qp, Y(Ⅱ) and ETR (P<0.05). The effect of water and nitrogen interaction on the fluorescence parameters of cotton in growing period reached a significant level (P<0.01). The effect of water and nitrogen interaction on Y, iWUE, NPFP and macron values reached a significant level (P<0.01). Among them, the maximum yield of seed cotton (Y) appeared in W2N2 treatment, as 5854.5kg/hm2;the minimum value appeared in W1N1 treatment, which was 3483.75kg/hm2, with a relative increase of 68.05%;through the multiple regression analysis and the likelihood function group, the optimal irrigation water and nitrogen application rate of the mild saline-alkali soil were 3740m3/hm2 and 754kg/hm2, respectively.