Abstract: Most of the bauxite resources in Lvliang mountain area are suitable for underground mining.As the price of bauxite continue to rise，bauxite had the condition of mining with filling.Filling mining is a new topic of mining technology in underground bauxite mine.The red mud waste that is produced during the production of alumina by Bayer process，is not available for large-scale filling in current technical conditions.Because underground bauxite mining engineerings are mostly arranged within the ore-body，the amount of waste-rock is insufficient.Filling mining in underground bauxite mines is faced with the problem of lack of filling aggregate.The exploratory test of filling aggregate is carried out.Loess is selected as the filling aggregate of an underground bauxite mine in Lvliang mountain area.The physical and chemical parameters，grain size analysis，slurry fluidity，bleeding rate and filling strength ratio of cemented loess are tested. The study results show that:①the loess slurry could be pumped into the stopes with past-like form；②industrial test results show that loess can be used as filling aggregate，when the cement-sand ratio is 1∶6，the filling slurry concentration not less than 68% and the bleeding rate is not more than 3%，the loess filled slurry is similar to the properties of paste and 28 d backfill strength not less than 0.8 MPa.The above study results further indicated that the loess filling meets the requirements of backfill strength and filling capacity of the underground bauxite，which is help for solving the problems of lack of filling aggregate and argillation of the watered roof and floor in stopes，besides that，it can also provide important technical support for controlling the ground pressure of bauxite mining and improving the recovery rate.

Key words: Underground mining, Underground bauxite mine, Filling mining, Loess, Similar paste filling