Efficient channel allocation is important for meeting the quality of service (QoS) requirements of both GSM voice calls and GPRS packets in integrated GSM/GPRS networks. In this paper, we propose a new dynamic channel allocation scheme with guard channel, channel de-allocation/re-allocation for voice call and packet queue for GSM/GPRS networks. An analytic model with general GPRS channel requirement is developed to evaluate the performance of the proposed scheme. Numerical results demonstrate that the scheme can adapt to different QoS requirements of the system by adjusting the number of guard channels and the size of packet queue. Compared to some conventional schemes, the proposed scheme achieves better performance of QoS provisioning.