The expired-time packet loss rate is a common parameter to measure the quality of service of transmission of deadline-constrained traffic in wireless networks. However, this parameter can not reflect the influence on the quality of service of video caused by the packets with different levels of importance. In this paper, the definition of the weighted expired-time packet loss rate is first introduced with the consideration of the importance of different kinds of packets, which describes the connection between the packet loss and quality of video more specifically. Based on the definition, an active queue management mechanism is proposed, which can be applied to deadline-constrained transmissions in wireless networks, and this mechanism, considering different levels of importance of video packets, drop packets actively to minimize the weighted expired-time packet loss rate during the service. Simulation results show that compared with the traditional queue management mechanism and real-time video filtering mechanism, the active packet discard mechanism can effectively reduce the weighted expired-time packet loss rate and improve the quality of service of video to about 0.5~1.5 dB Peak Signal to Noise Ratio (PSNR) gain.