Cloud　computing　and　Internet　of　Things　(IoT)　are　emerging　technologies　that　have　experienced　rapid　development　in　recent　years.　While　cloud　computing　presents　a　new　platform　over　which　services　are　offered　to　the　user　more　conveniently,　IoT　facilitates　the　collection　of　a　large　amount　of　data　via　interconnected　wireless　sensors　for　event　monitoring　and　control.　In　such　environments,　ownership　and　control　over　the　data　may　lead　to　potential　conflict　between　the　protection　of　data　and　the　provision　of　services.　Thus,　cloud　security　has　received　a　great　deal　of　attention　in　recent　years.　In　this　paper,　we　propose　a　method　for　trust　quantification　based　on　fuzzy　comprehensive　evaluation　theory　for　cloud　computing　to　protect　user　data　through　trust　quantification　of　cloud　services　after　we　introduce　trust　ontology　for　cloud　services　and　define　user　preference　trust　values.　By　enhancing　the　existing　trust　concept　based　on　dynamic　requirements,　we　introduce　some　cloud　service　attributes　to　study　layered　service　representation　for　trust　preference　and　then　apply　the　fuzzy　comprehensive　evaluation　theory　to　perform　trust　quantification.　We　also　perform　some　experiment　to　show　that　the　proposed　method　is　effective　and　can　dynamically　perform　trust　quantification　to　deal　with　malicious　acts　of　nonfaithful　services.