Push notification system plays an important role in the implement of enterprise office automation. And communication protocol and system architecture have become the main factors in the performance optimize of enterprise push notification system. Traditional standardized protocol scheme has encountered problems such as too complex to implement and huge traffic cost in mobile internet. This paper, for the stated problem and the features of enterprise push notification system, designed a communication protocol based on MQTT, a lightweight protocol in Internet of Things, and partitioned social network notification, instant messaging and presence by the design of MQTT topics. The new designed protocol is easy to implement and small traffic cost. On the other hand, this paper, based on the traditional symmetric and asymmetric system architecture, proposed a system architecture which is asymmetric on information and symmetric on function, by which supplied a detailed solution for push notification system for enterprise. This solution can meet the requirements of system design as well as improve the scalability of the system.