Adaptive cutoff priority is proposed for a multiple-server finite-capacity buffer system with two kinds of arrival streams in order to reduce the loss probabilities of both kinds of arrivals. It is shown that when the number of low-priority waiting customers is increased, the number of reserved servers for high-priority customers is adaptively decreased by using the adaptive cutoff priority. The state probabilities, which are functions of both the number of customers in the queue and the number of customers in service, are derived, and general expressions for the loss probability and the average queuing time are presented. The numerical calculations are carried out for the finite-capacity buffer system with adaptive cutoff priority and compared with those using conventional cutoff priority in which the number of reserved servers is always fixed. The theoretical results are ensured by the computer simulated results. It is shown that the total loss probability and loss probabilities of both arrivals can be reduced simultaneously if the number of threshold and the threshold values are appropriately selected.