Abstract: The effect of soil extracts with different pH values on the germination and seedling growth of 18 alfalfa varieties was investigated .The germination was inhibited under low or high pH of soil extracts. but when pH values were 6.17、8.76、9.20, the seeds had germinated could be promoted growth to some extent. The germination rate and ratio of seedling height to root length were regarded as two suitable acid and alkali resistance indexes, but the fresh weight was not. The proportion of germination in the substrate with pH values from6.43 to 8.44 was higher than 60%,and the seedling could grow normally. The critical pH was 5.06 or 9.17,and limiting pH was 2.71 or 10.26 through regression equation. Based on measured values, the 18 alfalfa varieties could be divided into 4 groups by AVERAGE cluster analysis. The results showed that Zhongmu No.1,Gongnong No.2 and Hopeland were most acid and alkali resistance.