In Wideband DS-CDMA system, increasing the utilization of Orthogonal Variable Spreading Factor (OVSF) code tree can serve more users. As Dynamic Code Assignment (DCA) does, the allocated codes will be reassigned when a new call can¡¦t be served even if the capacity is enough. However, reassigning occupied codes is expensive. In this thesis, we have proposed a state classification code assignment principle and a proportional reservation policy. In the proposed algorithm, the OVSF code tree is classified into four states. Then, the system will decide whether to reassign codes or not by checking the current state of the tree. In other words, the occupied codes will be reallocated in an appropriate occasion. Besides, we reserve vacant and available codes corresponding to the probability of requests for each supported rate when reassignment occurs. Therefore, the reassignment is reduced. It is also proved on the basis of the property of Markov Chain. Taking advantage of the proposed states classification code assignment and the policy of proportional code reservation, the call blocking rate and the number of reassignment can be reduced.