Abstract:Hairy roots of Cajanus cajan(L.) Millsp. was induced by Agrobacterium rhizogenes LBA9402 with direct inoculation. The optimum condition of induction of hairy roots in this test was as follows, the leaves of C.cajan were used as explants to be inoculated on 1/2MS solid medium, pre-culture for 2 d, the concentration of bacterium was OD=0.6-0.8, dissemination for 20 min, co-culture for 3 d, the rate of the hairy roots was 60%. PCR analysis at molecular level proved that T-DNA of Ri plasmid of A.rhizogenes 9402 has been successfully transferred into the genome of hairy roots of C.cajan.