Abstract: Systematical analysis on the failure causes of a reflux distributor of ethylbenzene /styrene separation tower was presented by means of macro and micro morphological observations, metallographic examination, chemical compositions analysis and mechanical test. The results indicate that the presentation of Cl- within the tower together with the stress co-acted and resulted in the stress corrosion cracking of the side plate of the reflux distributor. Finally the corresponding improvements and protective measures were put forward.