Abstract: Bacillus subtilis T2 is a potential biocontrol strain against a broad-spectrum plant pathogenic fungi. In order to determine special roles of extracellular protease in plant growth-promotion, deserted fish protein was selected as the only substrate to prepare degraded products of T2, acid-hydrolyzates and aqueous extracts, in which peptides and amino acids were included. Then, these three products were added to PG medium separately, and their effects on pakchoi root were investigated through observations under light microscopy and biochemical analysis. Results showed that within these three treatments, the hydrolysis protein products of T2 appeared to have the best function to increase root hair length, density, adventitious root formation and TTC reducing power. Content of L-tryptophan，which served as a precursor of indole-3-acetic acid (IAA), was much higher than other treatments. These results suggested that degraded products of Bacillus subtilis T2 could be a new biocontrol and plant-growth-promoting agent in the future.