With the frequent loss of pets, a pet-tracking system based on Message Queuing Telemetry Transport (MQTT) protocol is designed. The function realization of the system mainly relies on MQTT server, Web server and application program based on Android platform. The embedded device is made from a WZ-203CS demo board which integrates the MTK2503 chipset. With the help of the embedded IoT card, the device can transfer information about its location to Android mobile device under the MQTT protocol. Due to integrating the Amap navigation system, the application provides voice navigation, path planning, and other functions by processing the received information about location. Thanks to the basic structure, the system's function is not merely pet-tracking, but also has reserved interfaces for future uses, making the system more practical and has strong extensible at the same time.