The　adhered　mortar　attached　on　the　surface　of　recycled　aggregate　is　the　primary　difference　between　recycled　aggregate　and　natural　aggregate,　and　is　the　major　reason　for　reducing　its　mechanical　properties.　To　measure　the　percentage　of　adhered　mortar,　an　image　analysis　method　(IAM)　was　presented.　First,　three　comparative　specimens　were　conducted　to　demonstrate　the　precision　and　efficiency　of　IAM.　Further,　the　actual　adhered　mortar　content　was　also　studied　by　the　heating　and　cooling　method.　Then,　the　effect　of　recycled　aggregate　size　on　the　percentage　of　adhered　mortar,　and　the　characteristic　of　recycled　aggregate　was　explored　by　IAM.　In　addition,　the　type　and　optimal　size　of　recycled　aggregate　were　also　investigated.　The　obtained　data　indicated　that　IAM　is　an　accurate　and　efficient　method　to　measure　the　proportion　of　adhered　mortar　or　other　phases;　the　highest　content　of　adhered　mortar　was　found　in　recycled　aggregate　with　a　size　of　10.0-16.0　mm,　up　to　39.39%;　the　percentage　of　the　recycled　aggregates　with　a　particle　size　between　16.0　and　20.0　mm　should　be　increased　in　the　mix　proportion,　which　has　less　adhered　mortar　content　and　higher　quality　recycled　aggregate　content.