As a classical active queue management algorithm, compared with RED, BLUE has many advantages. It uses packet loss and link idle events to manage congestion. However, there are still some subtle drawbacks in parameter setting for BLUE, especially there is a significant change in the number of connections can cause the queue fluctuate between overflow and underflow. In this paper a new DT-based adaptive BLUE is proposed to improve the property of BLUE. The buffer is managed by dynamic threshold algorithm. The packet -dropping probability is determined by packet loss event, link idle event and the buffer usage ratio. The simulation results demonstrate that the proposed approach can effectively stabilize the queue occupation at a level and improve link utilization. It can mitigate the queue fluctuate which is caused by significant variety of connections.