This paper collects the guarantee network data of listed firms by using UNICET software，and surveys the effect of guarantee network on audit opinion.The results show that when a firm participates in guarantee network，it is more likely to be given a non standard audit opinion.When the firm participates in guarantee network to more extent，the size of network is larger，or the network is more complex，the firm in the network will be more likely to be given non standard audit opinion.Apart from paying attention to firm’s participation in guarantee network and the structure of the network，auditors also focus on the quality of the guarantee network.When the quality of network is better，the probability of being given non standard audit opinion is lower.These results indicate that as an important force of monitoring，the auditor has fully taken the information of firm’s participation in guarantee network into consideration and also takes it into the judgment of auditing risk.