In this study, the acoustic echo problem and cancellation method of Android-platform-based VoIP was analyzed and researched. The echo problem is consequential for Android phone-based VoIP applications. However, in the traditional 2G/3G circuit-switch (CS) mode, the acoustic echo is cancelled by the hardware chip, and the quality of communication is adequate. In the future 4G/LTE environment, all-IP packet communication will be achieved. The IMS/VoIP will become the main application for personal speech communication systems. Before the introduction of 4G with echo cancellation built into its chip, the Android-based VoIP on 3.5G/WiFi will continue to undergo the aforementioned acoustic echo problem. This paper presents an analysis of the acoustic echo on Android-based VoIP and proposes a simple echo cancellation method.