Based on the extensive collection of published data, the associated rare earthin aluminum- bearing rock series in bauxite deposits of China is studied, and the enrichment mechanism of associated rare earth is proposed. From the genetic type of the deposit, the content of associated rare earth in sedimentary type is the highest, followed by laterite type and accumulation type; in the distribution characteristics, the associated rare earth has obvious right leaning characteristics, belonging to light rare earth enrichment type; in the regional distribution, it has the distribution characteristics of “high in the north and low in the south”. The main aluminum- bearing rock series are different in REE content and rare- earth rich lithology, but the content increases gradually from top to bottom in profile. Ion adsorption, isomorphism and rare earth independent minerals may be the occurrence state of associated rare earth in aluminum- bearing rock series. However, due to diagenesis, the ion adsorption mechanism of associated rare earth in sedimentary bauxite is different from that in modern weathering crust of southern China. Compared with the rare earth content of bedrock and mineral composition of aluminum- bearing rock series, the pH value of sedimentary environment is the dominant factor for the migration and enrichment of associated rare earth in aluminum- bearing rock series. The formation of bauxite was accompanied by strong acid- base conversion in sedimentary environment. The frequency of conversion and the continuity of a certain state are different in the formation of different aluminum- bearing rock series, which affects the activity and migration distance of rare earths in the sediments, eventually lead to the difference in REE content and rare- earth rich lithology among different aluminum- bearing rock series.