In recent years, the negative impact of goodwill on business performance and enterprise value has attracted wide attention, but there is a lack of research based on audit. By taking A-share listed companies in Shanghai and Shenzhen from 2010 to 2019 as research samples, this paper empirically tests the impact of excess goodwill on audit opinion. The results show that the excess goodwill will significantly increase the probability of auditors to issue non standard audit opinions. The mediating effect tests show the operational risk and audit inputs are the action path. The heterogeneity tests indicate that the significant positive correlation between excess goodwill and non standard audit opinions is valid in the samples of private enterprises, lower quality of internal control, better institutional environment and higher analyst concern.