In a shared memory ATM switch with output queueing, queues share space flexibly in the common cell buffer. Buffer management schemes are needed to fairly regulate the sharing of memory among different output port queues. Of the conventional schemes. Static Threshold is simple but not efficient and does not adapt to the changing of traffic conditions. Pushout is the most efficient and adaptive scheme but very difficult to implement, Dynamic Threshold scheme combines the simplicity of Static Threshold and the adaptability of Pushout. In the VBR traffic, both high priority and low priority vells are generated. However, in Dynamic threshold, high priority cells are not protected when overload occurs. It consequently degrades the performance of the shared memory ATM switch. In this papwer, we propose a buffer management scheme which combines the Dynamic Threshold and the Non-Selective Pushout. This scheme is called an Advanced Dynamic Threshold. In this scheme, high priority cells are protected from being discarded when overload condition happens. When overflow occurs in the buffer, Non-Selective Pushout is applied