Risk assessment of leaching of pesticides at field scale level is of importance to protection of the groundwater environment. In this study, a total of 100 soil samples were taken from a field plot (27 m×27 m), which was located in the suburbs of Beijing. Some physico-chemical properties were analyzed of all the samples. By means of soil pedotransfer function, van Genuchten type's hydraulic parameters were generated from measured values of soil particle size fraction and soil bulk density using ROSETTA code. Dispersivities of atrazine were indirectly obtained from water retention curves, and adsorption coefficients of atrazine in different samples were estimated based on measured soil organic carbon content. And then, according to the column-model-based assumption, and with the aid of HYDRUS-1D software, the infiltration-redistribution process simplified from the actual background was simulated for evaluating the maximum risk of atrazine leaching through the unsaturated soil. The results show that, under the condition of a rainfall lasting 3 days with precipitation being 90 mm and intensity 30 mm d^-1 and 20 days of redistribution afterwards, if the effect of evapotranspiration on soil water movement and atrazine transport was negligible, the maximum cumulative amount of atrazine leaching down through the tillage layer (20 cm) was 17.87% and 75.41% of the applied dose, respectively, at the end of the infiltration and of the infiltration-redistribution processes, and spatial variation of the distribution of leaching flux of atrazine in the sampled area was quite different. The predicted vulnerable zone of atrazine leaching can not only provide quantitative basis for rationalizing use of the pesticide for the sake of environment protection, but also supply important information for preventing shallow groundwater from atrazine contamination.