The invention belongs to the technical field of biological 
catalysis, and relates to a biological preparation method of 
agmatine sulfate, which comprises the following steps: by using an L-
arginine sulfate solution as a substrate 
raw material, carrying out 
decarboxylation reaction in the presence of a biocatalyst and a coenzyme to obtain 
agmatine sulfate, and discharging gas CO2, wherein the biocatalyst adopts L-
arginine decarboxylase, and the coenzyme adopts phosphopyridoxal. The L-
arginine sulfate solution used as the substrate is stirred and mixed with the L-arginine decarboxylase and the coenzyme (phosphopyridoxal) to perform 
decarboxylation reaction under certain conditions, thereby obtaining the 
agmatine sulfate. The conversion rate is greater than or equal to 98%, and the 
continuous production yield can reach 90%. The technical 
route has the advantages of simple preparation technique, high production efficiency, low cost and the like. The 
fermentation and conversion techniques of the recombinant L-arginine decarboxylase can achieve the industrial preparation level, thereby basically solving the problems of high 
chemical synthesis cost, low yield, and great environmental hidden danger and the like.