The　heat　transfer　coefficient　of　composite　wall　with　fly　ash　blocks　sandwich　were　studied.　The　heat　transfer　coefficient　of　four　forms　of　wall　specimens　were　determined.　Based　on　the　basic　mechanism　of　the　thermal　conductivity　of　the　four　wall　types:　(1)　clay　bricks　wall;　(2)　clay　bricks　wall　with　fly　ash　blocks　sandwich;　(3)　recycled　concrete　bricks　wall;　(4)　recycled　concrete　bricks　wall　with　fly　ash　blocks　sandwich,　the　relationship　between　coefficient　of　thermal　conductivity　of　various　materials　and　temperature,　humidity　could　be　derived,　and　an　actual　value　calculation　method　for　calculating　the　heat　transfer　coefficient　that　suitable　for　engineering　design　was　also　proposed.　By　analyzing　the　experimental　values,　theoretical　values　and　the　actual　values　of　the　specimens,　the　actual　value　calculation　method　was　proved　to　be　correct　and　reasonable;　using　recycled　concrete　bricks　instead　of　clay　bricks　in　composite　wall　with　fly　ash　blocks　sandwich　the　good　insulation　effect　can　also　achived,　which　contributes　to　a　building　energy　efficiency　design　detailing　on　using　recycled　concrete　bricks　and　composite　wall　with　fly　ash　block　sandwich.　©,　2015,　Tongji　University.　All　right　reserved.