In order to explore the relationship between photosynthetic index and the variation of CO₂ concentration in the rhizosphere of cotton soils with different salinity contents, four different salinity treatments (CK:0%,F1:0.2%,F2:0.4%,F3:0.6%) were set, and the variation of soil CO₂ concentration and photosynthetic characteristics of cotton under two soil texture (sandy soil and loam soil) were studied in barrel cultivated cotton. The results showed that with the development of cotton growth period, the CO₂ concentration of the two soil textures both increased first and then decreased, and the peak values appeared at the flowering and boll stage, and the maximum CO₂ concentration was 17 061.95 μmol/mol in loam and 17 572.00 μmol/mol in sandy soil. Under the salt treatments, the soil CO₂ concentration of the two soil textures both increased with the increasing of soil depth. The average value of soil CO₂ concentration at 50 cm soil depth was 13 540.32 μmol/mol, which was nearly two times that of the surface layer at 10 cm depth. With the increasing of salinity content, the difference of CO₂ concentration between the two texture soils was significant, both of them showed a downward trend, and the CO₂ concentration of loam soil was significantly higher than that of sandy soil. The interaction between salinity content and soil texture had extremely significant effects on net photosynthetic rate (P_n) of cotton (P<0.01). Under the same soil texture condition, P_n of cotton showed a downward trend with the increasing of salinity content at different growth stages, and reached the minimum value in F3 treatment, but the effect of low salinity content on cotton photosynthesis index was not significant (P>0.05). Under the same salinity treatment, there was significant difference in P_n of cotton between different soil textures, showing loam > sandy soil. There was a close correlation between CO₂ concentration of two soil textures and cotton net photosynthetic rate under different salinity treatments, and cotton P_n could explain 81.2% of the variation of CO₂ concentration in rhizosphere soil, which indicated that salinity content and soil texture type affected soil CO₂ concentration through cotton net photosynthetic rate. The results could provide a theoretical reference for the growth environment of crop.