With the development and popularity of the mobile Internet and intelligent terminal, Instant Messaging once again become a hot field. However. Due to limitations of the mobile terminal device in a low power, low bandwidth and other aspects, it calls for higher requirements on Instant Messaging protocol. MQTT(Message Queuing Telemetry Transport) was designed as an extremely lightweight publish/subscribe messaging transport, and it is ideal for mobile applications. This paper introduced the basic content and features of MQTT, and gave a comparison with other instant messaging protocols such as SIMPLE and XMPP, then proposed a instant messaging solution of mobile terminal based on MQTT. Based on open source MQTT Broker Mosquitto, this paper also designed and implemented a instant messaging client for mobile terminal, and this client achieved instant message,presence,group functions and so on.