Chemical pesticide is toxic and not easy to be degraded to non-toxic compounds. The widely non-controlled usage of chemical pesticide had caused severer environmental problems, in addition, it can cause farmer’s health damage. Recently, bio-pesticide and bio-fertilizer (defined as agricultural biological agent here) has attracted more attention because it is environmental friendly. In general, bio-fertilizers add nutrients through the natural processes of nitrogen fixation, phosphorous solubilization, and stimulating plant growth through the synthesis of growth-promoting substances. Some probiotics have these functions and can be used as bio-fertilizer; in addition, they can also produce anti-bug/bacterial compounds and protect the plants. In conclusion, the agricultural biological agent combines the functions of pesticide and fertilizer.