Abstract. This paper introduces the performance analysis of VoIP applications over WLAN. The factors of VoIP quality include the voice codec, delay, jitter, and packet loss rate. The MOS and E-Model are sequentially considered as subjective and objective assessment of voice quality benchmark to study the relationship between voice quality and end-to-endpoint latency network dynamic environment through the establishment of the mathematical model. This study is also combined with the playout buffer algorithm mechanism to improve the quality of voice communications. In this paper, the researchers proposed a novel play algorithm with pareto distribution mechanism to measure delay, jitter and packet loss rate of VoWLAN voice quality by the MOS scores of different voice codecs. The simulation results proved that the novel adaptive playout buffer mechanism can reduce the latency, jitter, and decrease the packet loss rate and buffer requirements, and correspondently effectively improve the quality of VoIP voice.