Abstract: Choosing appropriate modifier as substitute of surface soil for scientific and reasonable improvement is the key for reclamation of overburden dumps in topsoil deficient area and adverse circumstances. Growth performance and stress resistance of crop is the response of the modifying effect. This experiment aims to research the effect of vermiculite to the growth performance and stress resistance of alfalfa and then evaluates its modifying effect on the cinnamon soil in mining area. In the experiment，single-factor with completed random is adopted. Local normal surface soil is used as control group and cinnamon soil as modified object. There are four parallel tests-0，10，30，50 g/kg vermiculite according to the added content of dry soil and each parallel test has three repeated experiment. The results showed that the vermiculite has obvious influence on the indexes of leaf area，plant height，root length，biomass，SOD activity，CAT activity，cell membrane permeability and so on（P＜0.05）at alfalfa seedling stage. But it has no obvious influence on content of chlorophyll and POD activity（P＞0.05）of alfalfa. It turns out that the growth performance and stress resistance of alfalfa do not have linear relation with added content of vermiculite. When the addition of vermiculite is 50 g/kg，it has the best improving effect on growth performance and stress resistance of alfalfa，and the best improvement for cinnamon soil.

Key words: Rehabilitation for overburdendumps, Surface soil substitution, Purple alfafu, Vermiculite, Open-pit coal mine