The telecom market has entered the stock development mode

which puts forward higher requirements for the operators’ stock user retention.Based on the concept of social network

this paper proposes a user retention method based on subnet model which different from the traditional "contractual" retention strategy for a single user.The concepts of communication subnet and viscous subnet are introduced

and the models of homogeneous subnet

heterogeneous subnet and susceptible nodes are constructed

which provide new ideas for the maintenance of operators’ stock users.