Abstract: Two kinds of models (Lagrangian model and Eulerian model) were established to investigate the origin of acid rain in Nanning. The spatial distribution of the sulfur deposition and area-to-area source-receptor matrix between Nanning and Guangxi autonomous region were calculated. The calculation result shows that 72% of sulfur deposition in Nanning comes from the external sources while 28% comes from local sources in 2001. Therefore, external sources play major role in formation of acid rain in Nanning. According to simultaneous pH monitoring by environmental monitoring stations of Guilin, Liuzhou, Wuzhou and Nanning for 10 rainfalls from August 2001 to September 2002, the largest contributors of sulfur deposition in Nanning were still external sources. This shows that the calculation results by the two models are reasonable and credible.