To guarantee the quality of service (QoS) for multi-services as well as achieve optimum utility of valuable bandwidth in wireless networks, an effective call admission control is urgent. However, the variety and complexity of traffic, the various requirements of bandwidth and QoS guarantee make it a complicated problem. Recently, the dynamic call admission mechanism was found to be more stable and precise. But, it is still hard to get an effective dynamic call admission mechanism for multi-services. Most of the relative studies cope with this problem by setting up a multiple dimensions? stochastic model with high computational complexity. In this paper, we found it is enough to use the simplified single dimension stochastic model to compute the key parameters, such as call dropping probability and admission probability. In addition, a fast numerical method has been found to decrease computational complexity. Numerical results of simulation show that the proposed scheme named OSCA steadily satisfies the hard constraints on call dropping probability for multi-services while maintaining a very high channel throughput.