In order to detect the dynamic changes of soil fertility and salt alkali and their effects on wheat yield, the newly reclaimed farmland (10, 20, 30, 40 and 50 years) in the south margin of Tarim Basin were taken as the research object, and the uncultivated desert natural soil was taken as the control, the soil properties, such as organic matter, nutrient and salt alkali of the surface soil (0-40 cm) were measured. The results showed that the organic matter content in the surface soil (0-20 cm and 20-40 cm) increased linearly with the extension of cultivation time, but the change range of organic matter content in 20-40 cm soil layer was relatively small. In the 0-40 cm soil layer, the changes of the total nitrogen, available nitrogen and available potassium content with time extension were all significantly positively correlated with organic matter content, which increased by 88.8%, 213.4 and 37.5% in 50 years of reclamation respectively compared with that of the native desert soil. Available phosphorus content increased linearly in the initial 30 years after cultivation and then decreased. However, it increased by 1 201.2% in 50 years after cultivation compared with the uncultivated soil. The nature desert soil was mildly salinized soil dominated by Na⁺ and Cl^-. The total salt content decreased sharply after cultivation, and the difference between different years was not obvious, and the average value of which was 0.8 g/kg in 0-40 cm soil layer. The dominate cation and anion of the cultivated oasis farmland changed to be Na⁺ and HCO₃^-. The pH value increased by 13.4% in the initial 30 years (pH 8.85) compared with the desert soil, and then decreased significantly. The change of pH was positively related with accumulation of CO₃^2- and K⁺. The average wheat yield in the new reclaimed farmland was 4.79 t/hm², and which was negatively related to the content of Na⁺ and Cl^-, but was not related to the content of soil organic matter, nutrients and total salt as well as pH value. In conclusion, continuous cultivation significantly improved soil fertility and salinization degree. However, the wheat yield was closely related with the content of Na⁺ and Cl^- in 0-40 cm soil layer. The results suggested that fertilizing oasis farmland soil and taking effective measures to reduce Na⁺ and Cl^- content from rising again were important to achieve stable and high yield of wheat in the study area.