This study aimed to quantitatively analyze the yield effect and synergistic effect of straw mulch and nitrogen on spring wheat in dry land. By use of the APSIM model, the crop yield of spring wheat were set 25 treatments were simulated by using the model with 5 gradients over the two variables, straw cover and nitrogen application. The wheat field experiment was performed in Anding District, Dingxi City, Gansu Province from 2016 to 2018, and the measured values of spring wheat yield were collected in the three sowing periods(ESW, NSW and LSW). APSIM model was used to simulate the simulated values of spring wheat from 2016 to 2018, and the simulated values were compared with the measured values to analyze the applicability and simulation accuracy of the model. The coupling relationship between spring wheat yield, straw mulch amount and nitrogen application amount was analyzed by quadratic multinomial regression and path analysis, and the maximum spring wheat yield and the corresponding straw mulch amount and nitrogen application amount were calculated by Matlab. The results showed that both the simulated and measured yields under different treatments were within the 15% confidence band, and the simulation accuracy of the model was high, with the normalized root mean square error(RMSE) ranging from 4.64% to 12.22%, indicating that the model had good applicability in the study area. The increase of straw cover amount and nitrogen application amount had a positive effect on spring wheat yield, which showed a quadratic parabolic relationship of opening downward. Under ESW, NSW and LSW simulation, the maximum yield of spring wheat was 3 548.64, 3 149.59 and 2 507.58 kg/hm2, respectively. The optimal combinations of straw mulch and nitrogen application were 7 062.04, 194.91 kg/hm2 and 8 211.31, 218.81 kg/hm2 and 6 215.15, 162.01 kg/hm2, respectively.