Abstract
In this paper we consider the network formation problem of social networks. In this model, every vertex is asked to establish an edge with the second neighbor with a probability on the Erd˝os-R´enyi model and the configuration model respectively. We call this operation triad formation. We derive the mean degree, degree distribution and the clustering coefficient of these two models. Here, we use two parameters to match the networks of given mean degrees and clustering coefficients simultaneously.