It is an important issue to distinguish the credibility of information in this era of information explosion so that users can have a reference for judging unknown information. Using the method similar to the PageRank of the importance of web pages, we compute the score ``TrustRank'' to solve the problem about which information should be trusted. We create a forum to verify the effect of TrustRank method. We also solve the ``rank sink'' problem while doing the computation on TrustRank. We not only use TrustRank to analyze which information can be trusted, but also use different quantities of data which can be collected in the forum to analyze. Moreover, we design an efficient method to estimate the TrustRank.