Abstract: The Kirirom bauxite deposit, as a typical weathering-leached lateritic bauxite deposits, with the characteristics of large reserve and good quality, is an important deposit in indochina peninsula lateritic bauxite belt.There has no publishes about its elemental composition due to the low degree of geological study.Reported here are the main elemental composition and rare earth elements (REE) data of two different weathering occurrences and their underlying basalts, to discuss the genesis of bauxite in this area.The results show that, the bauxite ores have a character of low REE content in general (ΣREE=34.22×10^-6～102.17×10^-6，locally 225.92×10^-6), and the metallization shows elements migration with an uneven distribution.The LREE/HREE values (4.73～22.73) and (La/Yb)N values (5.61～36.22) are high, the fractionation of LREE and HREE is obvious, shows LREE enrichment, and the stronger the weathering, the more obvious fractionation.The REE distribution pattern is characterized by flat right inclining type with weak Eu positive abnormal (δEu=1.04～1.11), and the difference of Ce abnormal in different occurrence shows as that the weak negative Ce abnormal in less weathering occurrence and weak positive Ce abnormal in stronger weathering occurrence.Similar REE distribution patterns and δEu between bauxite and basalt as well as the δEu- TiO₂/Al₂O₃ graphic indicate that the basalts are the material source of bauxite ore in this area; The stronger weathering occurrence shows high contents of Al₂O₃, indicates that grade and quality of the bauxite is closely related to the weathering progress.