Efficient resource allocation for multi-class traffic with QoS guarantee is an important issue in integrated multimedia mobile communication networks. In the third generation mobile communication systems, the Orthogonal Variable Spreading Factor (OVSF) codes are used as spreading codes. The use of OVSF codes allows the spreading factors to be changed for variable bit-rate requirements. In this paper, we presented the code- based guard channel schemes and analytical models for QoS management in W-CDMA systems. Compared with traditional channel-based schemes, the proposed schemes and analytical models exactly reflect the restrictions of OVSF code tree characteristics and are suitable for W-CDMA systems. From the illustrations and numerical results, we find that the proposed model is easy to construct and to analyze QoS management schemes in W-CDMA systems. It can also be extended to more complicated multi-class traffic types systems.