A　simple,　rapid　mathematical　model　to　calculate　the　non-steady-state　startup　process　of　the　jacket-type　radial　heat　pipe　is　presented　in　this　paper.　The　model　is　based　on　the　special　structure　and　using　conditions　of　the　jacket-type　radial　heat　pipe,　the　vapor　temperature　in　heat　pipe　only　changes　over　time.　The　startup　performance　of　the　heat　pipe　with　variation　input　heat　flux　and　the　filling　rate　is　analyzed.　The　results　manifest　that　the　filling　rate　increased　will　reduce　the　maximum　operating　temperature　of　the　heat　pipe　and　shorten　the　startup　time　of　the　heat　pipe.　With　the　increase　of　input　heat　flux,　the　operating　temperature　increases　and　the　time　to　reach　the　steady　state　of　the　heat　pipe　is　added.　The　total　thermal　resistance　of　heat　pipe　decreases　with　the　increase　of　the　input　heat　flux　and　filling　rate.　The　variation　of　the　local　convective　heat　transfer　coefficient　and　the　maximum　temperature　of　the　water　are　investigated　with　different　cooling　water　inlet　conditions.