Abstract: To determine the effect of temperature fluctuation on spring wheat grain yield in drylands, a 2 × 9 factors design of daily minimum and maximum temperatures was set up. The spring wheat yield was simulated using the APSIM (Agricultural Production System Simulator) model under various conditions. Quadratic polynomial regression, single factor marginal effect analysis and path analysis were used to investigate the response of spring wheat yield to changes in daily minimum and maximum temperature. The results showed that the biggest increase in spring wheat grain yield was 1.40% (average of 1.34%) when daily minimum temperature increased by 0.25 ℃ with constant maximum temperature. Increase in minimum temperature had a positive effect on spring wheat yield. The biggest decrease in spring wheat grain yield was 2.88% (average of 2.42%) when daily maximum temperature increased by 0.25 ℃ with constant minimum temperature. Increase in maximum temperature had a negative effect on spring wheat yield. The best fit curve between spring wheat yield and maximum temperature was quadratic parabola, which indicated a decreasing tendency with increasing maximum temperature. The synergetic effect between minimum and maximum temperature on spring wheat yield was negative. The negative effect of increased maximum temperature on spring wheat yield was greater than the positive effect of increased minimum temperature on spring wheat yield. Thus decrease in spring wheat grain yield was mainly due to increase in maximum temperature.