Chromosomal virulence genes acvB, abvA, chvA of Agrobacterium tumefaciens were cloned with the technique of transposon 5 insertion. The chromosome genes are necessary for Agrobacterium tumfaciens absorbing to cell ular surface of plant, the adherence reaction can't be executed and result in losing the toxicity if mutations are occurred in some chromosome genes. The chromosome toxicity gene is inactivated due to transposon Tn5 be inserted and the accept ant cell infected with Agrobacterium tumefaciens can't cause tumor ultimately. This article briefly introduces the research way of thinking and strategy of this technique and the important roles of every gene, which are taken of in the process of T-DNA's form, transfer, integration, and expression etc. This article also gives a presumption to T-DNA's transport: The plant cell wall's porin may be T-DNA's natural channel.