Abstract: A thorough understanding of pressure and discharge along lateral is needed for efficient design and operation of subsurface drip irrigation (SDI) .Test data and distribution of pressure and emitter discharge were obtained by using shorter lateral based on the experiment plan of SDI lateral hydraulic factors .The nonlinear equations describing lateral pressure, emitter discharge and local head loss factor coefficient were established based on the test data and research results of single emitter hydraulic characteristics in SDI. Calculation of nonlinear equations had been translated into the function optimization problem, and the optimization mathematical model was established, the genetic algorithms was adopted to solve the model. The calculated result was validated by test data, and it indicated that the distribution of pressure and discharge along SDI lateral could be described with the nonlinear equations and solution method had the high calculation accuracy. This method lays the foundation of further study the hydraulic factors of SDI lateral.