The　insulation　layer　is　usually　installed　in　the　tunnel　structure,　whereas　the　influence　of　the　insulation　layer　on　the　thermal　behavior　of　energy　tunnel　ground　heat　exchangers　(GHEs)　is　rarely　investigated.　The　model　tests　were　performed　in　this　study　to　evaluate　the　heat　transfer　potential　of　the　energy　tunnel　with　the　insulation　layer　under　ventilation　and　groundwater　seepage.　The　results　can　be　obtained　as　follows:　first,　the　fluctuations　of　air　temperature　and　surrounding　rock　temperature　at　different　locations　are　relevant　to　insulation　layer,　ventilation,　and　groundwater　seepage.　Second,　the　reduction　effect　of　ventilation　on　the　interface　temperature　of　tunnel　lining　and　surrounding　rock　is　alleviated　when　using　an　insulation　layer,　and　the　interface　temperature　at　upstream　section　of　groundwater　seepage　is　more　easily　affected　by　the　energy　tunnel　GHEs.　Third,　the　variation　range　of　ground　temperature　is　wider　at　the　downstream　section　of　groundwater　flow.　Moreover,　the　heat　exchange　rates　of　tunnel　without　the　insulation　layer　improve　by　5.82%　and　6.45%　with　increasing　wind　speed　at　two　groundwater　flow　velocities　of　1x10(-4)　and　5x10(-4)　m/s,　and　there　are　only　2.03%　and　0.77%　enhancements　of　heat　exchange　rates　by　ventilation　for　the　tunnel　with　the　insulation　layer.　However,　the　thermal　performance　of　the　energy　tunnel　improved　by　groundwater　is　less　relevant　to　the　existence　of　the　insulation　layer.　The　relevant　findings　can　provide　an　effective　guidance　for　the　following　research　and　design　of　the　energy　tunnel.