The paper gives detailed comment on the paper of Variation of REE content in shear zone and its mechanism———Exemplified by the ductile shear zone on the northern margin of Jiaonan orogenic belt", published in this magazine in 1998. Combined with the results of mobility of REE in various geological environments and the element migrations effected by fluid flowing in the ductile shear zones, the author expounds that fluid infiltration and rock volume loss are controlled factors of REE variation in the process of ductile shearing.