The Quality of Service (QoS) term is refer to capability of network to prioritization and service distinguish for providing better service to some service classes and call types. Because of the lack of resources, from one side, and user's mobility from the other, provision of QoS guarantees is considered at the head of the challenges that wireless cellular mobile network systems face. Call Admission Control (CAC) is used for providing and achieving QoS guarantees in wireless systems. This paper proposes a new CAC algorithm with priority index for providing and achieving QoS guarantees on the call level in wireless systems in terms of new call blocking probabilities using multiple thresholds to determinate the number of acceptable new calls of each type of service. Results of simulation provided in this paper show that the application of proposed new CAC algorithm with priority index on the New Call Bounding Scheme (NCBS) provides a new CAC scheme which has better performance in terms of new call blocking Probabilities and guarantees any desired level of QoS for new call types with the keeping priority of handoff calls.