This paper considers the transmission performance of multimedia streams, especially Scalable Video Coding (SVC), over mobile WiMAX networks. SVC supports temporal, spatial, and quality scalabilities at bit-stream level, which enables the easy adaptation of video by selecting the sub-sets of bit-stream. Thus, SVC streams are more suitable than non-scalable bit-streams in the mobile environment where network conditions are dynamic. In this work, we firstly set up a simulation platform, which integrates NS-2 WiMAX module with EvalSVC evaluation tool set. Then, we design scenarios involving multiple Mobile Stations (MS) and handover to evaluate the performance of video streaming. After intensive simulation tests, we compare the throughput and the packet delay in the different connection scenarios, and count the frame loss of the received video. The simulation results indicate that, in terms of frame loss, the number of MSs is critical to the performance of video transmission. Moreover, handover imposes great influence on video stream transmission.