The current water-carbon coupling models have several issues such as complex mechanisms,unbalanced structure,large uncertainty,and difficulty to meet the information needs.According to the concept offrom the complex phenomena,find a simple rulefrom the nonlinear hydrological cycle simulation theory,a nonlinear water-carbon coupling model was developed based on the nonlinear system theory of the hydrological cycle and Jarvis stomatal conductance method.The experimental data at the Duke station of American-Flux and in the Chongling experimental watershed of the upstream of Baiyangdian were used to verify the model accuracy at the point and watershed scales.The results indicated that the nonlinear water-carbon coupling model can simulate the variations of evapotranspiration and soil moisture reasonably and accurately.The model was applied to estimate the effects of greenhouse gas discharge level on the hydrological cycle elements.When the concentration of carbon dioxide increases,the increase of runoff is 0.5%,increase of average soil moisture is 1.2%,while decrease of evaporation is 4.9%.Overall,the water-carbon coupling model achieves a simple solution to solve the complex problems.