Abstract:The influences on the viable count of freeze-dried Lactobacillus plantarum CGMCC 6016（L.P.dy-1）during storage by different cryoprotectant were studied.And the fermentation activity of freeze-dried L.P.dy-1 affected by cryoprotectant was analyzed with the flow cytometry method （FCM）.The results were as follows：10 % of inulin，22.4 % of inulin，inulin composite protective agent and skim milk composite protective agent were used as cryoprotectant to protect the freeze-dried L.P.dy-1.The viable count of L.P.dy-1 was still higher than 1010 CFU/g after 8 months stored in-20 ℃，while only the viable count of inulin composite protective agent group kept a level higher than （0.94±0.17）×1010 CFU/g after 8 months stored in 4 ℃.The freeze-dried LAB with cryoprotectant could keep high acid production activity storage in-20 ℃ for 6 months and 4 ℃ for 4 months respectively.Among the cryoprotectant groups，the cell activity of the inulin composite protective agent group has the slowest decline.The correlation degree R2 between the results of pH value and FCM was 0.77，which indicated that FCM was suitable for the study of cell activity of freeze-dried L.P.dy-1.Compared with the freeze-dried L.P.dy-1 added with skim milk composite protective agent，the bacteria prepared with inulin cryoprotectant could keep a higher fermentation activity and similar cell proliferation activity with the direct activation group.