Abstract: In order to improve the stability of microbial agents with Streptomyces silaceus SN16，the amounts of carriers，protectants and dispersants were optimized and the optimal formula of them was determined，and the influence of which on wheat seedling growth was studied by pot experiment. Results showed that the optimal formula of the microbial agent was Streptomyces SN16 20%，sodium alginate solution（1 mg/mL）24%，sodium carboxymethyl cellulose（CMC）solution（10 mg/mL）24%，and diatomaceous earth 32%. By this formula，the biomass of microbial inoculum was 2.45×108 CFU/g while conserved at 4℃ and 0.94×108 CFU/g at room temperature after 60 d. Pot experiment demonstrated that the plant height，fresh weight and dry weight of wheat seedlings applied with microbial agent of 1% Streptomyces silaceus SN16 increased by 9.85%，57.90% and 66.67% compared to the CK，respectively，which reached significant level（P<0.05）. However，its promoting effect on root was insignificant（P>0.05）. This research provides a new type of Streptomyces silaceus agent for agricultural production.

Key words: Streptomyces silaceus, microbial agents, additives, wheat, seedling growth