Aerosol optical depths (AODs) are calculated for the Xi'an region based on the observation data of a sky radiometer (POM-02) and Beer-Lambert-Bouguer law. These AODs are used as true values to compare with three inversion algorithms' results of AODs in the MODIS C061 product of NASA Terra satellite, and the accuracies and applicability of those three inversion algorithms for the Xi'an region are discussed. Furthermore, we statistically analyze the spatial distributions and seasonal variation characteristics of AODs for the Xi'an region and its surrounding region using MODIS aerosol products. The results indicate the following: there is the best relationship between the AODs inverted from the MODIS DT&DB product and POM-02 data among those three MODIS inversion algorithms of Terra satellite, and its correlation coefficient is approximately 0.92. Thus, the MODIS DT&DB product is the most appropriate product for studying climate change and air pollution in the Xi'an region. Dust storms and human activities are the main sources of aerosols in the Guanzhong Plain. The AODs are greater in the eastern part and less in the western part of Guanzhong Plain, and the high-value centers are mainly distributed in the regions such as Xi'an, Xianyang, and Weinan. The AODs in the Xi'an and Xianyang regions reach their maximum and minimums in the spring and autumn, respectively. However, the AODs from other regions in the Guanzhong Plain show apparently seasonal variation characteristics with greater values in spring and summer and lower values in autumn and winter.