This paper reviews, the allelopathic research status of hemp (Cannabis Sativa L.), and its insecticidal, herbicidal and bactericidal activities. There are numerous active chemical components (mainly secondary metabolites) and their derivatives possessing special effects in hemp plants. These belong from various chemical classes: cannabinoids, flavonoids, stilbenoids, terpenoids, lignans and alkaloids etc. and their derivatives, many of these have strong allelopathic effect on crops, weeds and microorganisms. Its herbicidal allelopathic compounds (e.g., stilbenoids, terpenoids, lignans and alkaloids etc.) may be developed as ecofriendly herbicides to reduce reliance on synthetic herbicides.