Irrigation plays an important role in agricultural development, in which underground water environment is the important part. This article develops a random simulation mathematical model of underground water environment under different boundary conditions. The model can be used for simulation of underground water table, solute transport and groundwater accumulation. The simulation methods of precipitation, evapotranspiration and other random variables are analyzed, and dynamic simulation is carried out on the above random factors by using random time-series theories. VISUAL MODFLOW software is used in this article. The model and the methods are used in Jiangxi Gandong irrigation district, with a total area of 201.38km(2). Results indicate that the maximal relative error between simulation values and observation values of water table is 2.38%, and total nitrogen concentration is 11.67%. The model deduces, simulation curves of groundwater table and simulation curves of total nitrogen at characteristic spots for 30 years, and feasible area rate of water surface and the maximal annual recharge of contamination are put forward. The results will offer a guidance on the planning of water conservancy engineering and the corresponding administration for similar regions.
