Preliminary　experimental　study　on　flow　pattern　and　pressure　drop　of　gas-liquid　two　phase　flow　of　micro　pin　fin　heat　sink,　using　nitrogen　and　de-ionized　water　as　working　liquid,　has　been　carried　out　in　this　paper.　The　result　shows　that　surface　tension　effect　plays　a　major　role　when　the　flow　rates　of　gas　and　liquid　are　both　low.　And　the　bubbles　stagnate　between　the　fins　randomly　in　this　stage.　The　value　of　C　in　Chisholm　correlation　undergoes　two　evolvement　processes,　which　are　caused　by　the　change　of　surface　tension　effect　and　flow　pattern,　respectively.　The　M-H　model,　which　is　only　considered　the　effect　of　equivalent　diameter,　agrees　well　with　the　current　data(a　mean　deviation　of　9.27%).　In　low　liquid　flow　rate　the　L-Mu　model　can　predict　experimental　data　accurately.