The　development　of　cloud　computing　technology　and　the　popularization　of　cloud　services　have　a　great　impact　on　the　industry.　On　the　one　hand,　cloud　technology　enhances　network＇s　operation　efficiency　and　reduces　the　cost.　On　the　other　hand,　the　cloud　resource　can　be　accessed　by　any　network　equipment.　It　increases　the　chances　that　the　identity　of　user　is　misrepresented　and　then　led　to　many　security　problems.　Therefore,　the　actual　needs　of　security　can＇t　be　fully　satisfied　with　controlling　the　malicious　user　access　to　the　cloud　resource　by　login　authentication　that　relies　solely　on　current　user　identity.　User　is　the　requester　and　provider　of　cloud　resources.　User　behavior＇s　credibility　relates　to　the　safety　of　cloud　directly.　So　it＇s　very　important　to　evaluate　whether　user　behaviors　can　be　trusted　or　not　on　cloud.　In　this　paper,　the　method　is　studied　based　on　the　multilevel　fuzzy　comprehensive　evaluation.　And　in　this　evaluation　study,　indicators　of　user　behavior　credibility　are　carried　on　a　thorough　discussion.　©　2017　ACM.