A　model　was　built　for　the　gap　acceptance　using　the　analysis　method　of　logistic　model　to　describe　the　driver　behavior　of　gap　acceptance　and　rejection　in　the　upstream　transition　area　to　study　the　gap　acceptance　of　merging　in　the　expressway　work　zone.　Merge　probability　of　driver　accepted　gap　was　studied　in　gap　acceptance　model　and　6　independent　variables　were　selected　from　merging.　It　was　found　that　2　independent　variables,　the　back　relative　headway,　vehicle　speed　of　being　overtaken　were　significantly　related　to　merge　probability　based　on　actual　data　and　mixed　step-by-step　selection　method.　The　proposed　logistic　regression　model　was　tested　on　the　fittness　and　predictive　accuracy　and　the　encouraging　result　was　achieved.　A　critical　gap　calculation　formula　was　derived　from　the　gap　acceptance　model.　The　conclusion　provided　technical　support　for　the　design　of　upstream　transition　length,　traffic　organization　and　management　of　the　work　zone.