The origin of Quaternary red earth in Jiujiang and Taihe, Jiangxi Province had been discussed by comparatively studying on the forming environments, the particle-size distribution, the geochemical characteristics of REE and the morphological features of the quartz grains. The results showed that the Quaternary red earth in Jiujiang, located in the transitional zone between red earth and Xiashu loess, was aeolian origin, as it shared many aeolian features with Xiashu loess; however, that in Taihe, located in the Ji'an-Taihe Basin, was alluvial origin, with obvious alluvial features.