In the traditional water movement model of the furrow irrigation based on water balance method, it is necessary to determine the value of the figure coefficient of infiltration water (σz) before simulating water flow of the furrow irrigation, which affected the precision of the model. The relationship between the figure coefficient of infiltration water and water flow under furrow irrigation was analyzed, an analytic model of furrow irrigation on the basis of water balance method was set up, and the iterative algorithm to the analytic model was determined. The influence of different σs values in 0.70～0.80 on the model compute results was studied, the model results were verified with some research results and field experimental values. The results showed that the problem of getting σz directly with difficulty was solved and the accuracy of the model was improved. It is also found that different σs values in 0.70～0.80has little influence on the model compute results and when the σs value is 0.75, it has better accuracy for the model than that when the σs value is 0.70 or 0.80. The study indicated that the analytic model has some advantages, such as simple calculation method and solution, high accuracy. 