This paper proves multicast management belongs to problems of HDP, provides the cost analytical model of multicast logical key tree which applies HDPT. Based on the above analysis, the author proposes an improved multicast logical key management scheme termed as L-R logical key tree management scheme. L-R logical key tree management scheme is a kind of imbalanced multicast logical key tree, which is based on periodic re-key, according member nodes’ joining and leaving different probability, it employs different multicast key management strategy. The paper provides the design and calculation of the scheme, and realizes it in a simulation. By comparing this scheme with the typical LKH one, it shows clearly the scheme proposed in the paper is of high effect and low cost.