Though privacy and trust have been studied in the social network site (SNS), few have identified the relationships among users’ privacy concern, trust and their actual usage behavior in SNS. Moreover, little attention has been paid to investigating the differences between users from different cultural contexts. In this paper, we have been engaged in addressing these concerns by surveying two typical user groups. The analysis of their answers showed that French and Chinese are not only significantly different regarding privacy and trust belief in SNS, but also act significantly different in disclosing personal information, posting messages, and developing new relationships. Furthermore, the effect of privacy concern and trust on users’ visiting frequency and willingness to meet new people is also found different between the two groups.