Paenibacillus sp.MY03 is a bacterium with high agarase activity which has been isolated from the soil of cypress roots.In order to promote the exterior agarase development,growth conditions of MY03 strain have been optimized.As a result,60 hours after its fostering at 37℃,with the inducer of agar powder at a concentration of 0.05% and the starting pH of 7.0,MY03 strain shows a high stability of agar-producing,which might be helpful for deep research of agarase and the encoding of genes.