Aiming　at　the　shortages　of　constraints　solving　in　collaborative　design,　an　interval　narrowing　algorithm　based　on　constraint　bintree　was　put　forward,　in　which　two　processes　were　included,　namely　the　forward　interval　expanding　operation　from　bottom　to　root　of　constraint　bintree　and　the　backward　interval　shrinking　operation　from　root　to　bottom　of　constraint　bintree.　Then　a　constraint　solver　has　been　developed　to　solve　the　public　solution　space　of　the　multi-disciplinary　constraints.　Using　this　method　can　avoid　introducing　the　internal　variables　and　decomposing　the　constraints　into　solution　functions,　improve　solving　efficiency　and　easily　implement　symbol　calculation　automation.