Social networks have become valuable resources of big data exploration for individual users as well as for researchers and commercial organizations. However, how to protect user privacy while assure data credibility at the same time is still a big challenge both in practice and in academic research. This study presents a social network model for the purpose of big data privacy preserving and credibility assurance. In this paper, we discuss the mechanism of the model and present practical implementation designs on achieving the goals. Applications of the model in healthcare social network are also discussed.