Air　side　heat　transfer　and　fluid　flow　characteristics　of　two-row　slotted　fin-and-tube　heat　transfer　surface　with　X-type　strip　arrangement　were　studied　experimentally　and　numerically.　The　heat　transfer　and　friction　factor　correlations　were　obtained　in　a　wide　range　of　Reynolds　number.　It　is　found　that　the　slotted　fin-and-tube　heat　transfer　surfaces　have　excellent　performance　compared　with　the　plain　plate　fin　heat　transfer　surfaces　and　the　performance　of　X-type　two-side　strip　fin　surfaces　is　better　than　that　of　one-side　strip　fin　surfaces.　By　numerical　method,　the　fin　efficiency　curves　for　X-type　two-side　strip　fin　surfaces　were　achieved.　From　the　viewpoint　of　field　synergy,　the　air　velocity　and　temperature　fields　between　the　two　neighboring　fin　surfaces　and　the　distribution　of　local　heat　transfer　coefficient　and　pressure　drop　in　flow　direction　were　analyzed.　The　results　show　that　the　heat　transfer　enhancement　of　slotted　fins　is　caused　by　the　improvement　of　the　synergy　between　the　velocity　field　and　the　temperature　gradient.