Dansyl chloride was used as derivative reagent and 1,7 amino heptyl amine was used as internal standard to verify the " GB /T5009. 208-2008". The soybean was chosen as raw material to find the change rule of amino nitrogen and biogenic amine of Douchi in the process of natural fermentation. The results showed that there were eight kinds of biogenic amines in natural fermentation process as follows: histamine,tryptamine,beta phenethylamine,putrescine,cadaverine,tyramine,spermine and Spermidine. After 72 h of fermentation,the content of tyramine rose to the highest( 488 mg /kg),the content of tyramine and amino acid nitrogen were greatly increased first and then slowed down gradually. Refer to the relevant provisions,it was found that the contents of histamine and tyramine which had the main toxic effect were not higher than the country maximum allowable range,so in theory there was no potential safety hazard in bacteria-fermented Douchi. And it should be noticed that the rising trend of histamine content may cause potential safety hazard,so the natural fermentation time of bacteria-fermented Douchi should be controlled.