As one of the three mainstream technologies in the 3rd generation mobile communication IMT-2000, WCDMA uses OVSF as its channelization codes, which can support a variety of rate requests. The variable length feature of OVSF codes can meet the multirate traffic requirements in communication, and its orthogonal nature can reduce the mutual interference between channels. This paper studies OVSF codes and verifies the orthogonality of OVSF codes in theory through MATLAB simulation. It introduces the single-code assignment, dynamic code assignment and the dynamic code assignment fulfilling different QoS requirements by stage. It also compares the system throughput and code blocking probability of each single-code assignment algorithm by simulation to verify the performance of various algorithms.