The invention relates to the field of pesticides, and discloses piperazinone derivatives, a preparation method thereof, an inhibitor, and a method for preventing and controlling root parasitic weeds.The piperazinone derivatives have a structure represented by a formula (I) shown in the description, wherein R<1> is cyclohexenyl, norbornyl, norbornenyl or adamantyl, R<0> is a group having a structure represented by a formula (II), a formula (III) or a formula (IV) shown in the description, R<2> is methylene, methine, difluoromethyl, amino or phenyl, R<3> is an oxygen atom, and R<4> is substituted or unsubstituted phenyl, substituted or unsubstituted p-(methylsulphonyl)tolyl, substituted or unsubstituted phenoxy, substituted or unsubstituted naphthyl, a substituted or unsubstituted group shown in the description, a substituted or unsubstituted group shown in the description, or substituted or unsubstituted pyridyl. The piperazinone derivatives provided by the invention have high stability, can efficiently inhibit activity of striga asiatica receptor proteins, and can inhibit germination of root parasitic weed seeds in the presence of strigolactone analogue GR24.