Numerical　simulations　and　analysises　were　presented　on　heat　transfer　characteristic　for　combined　micro　pin　fins　heat　sink　which　consisted　of　circular　pin　fins　with　isosceles　right-angled　triangle　pin　fins　on　both　end　sides.　The　numerical　results　were　analyzed　according　to　different　attack　angle　arrangements　of　right-angled　triangle　pin　fins.　Comparing　with　micro　circular　pin　fin　heat　sink,　the　heat　transfer　for　combined　micro　pin　fin　heat　sinks　is　improved　greatly.　In　addition,　the　computational　evaluations　indicate　that　the　heat　transfer　enhancement　effect　of　combined　micro　pin　fin　heat　sink　with　the　attack　angle　30°　is　the　most　significant.　However,　the　heat　transfer　enhancement　effect　is　decreased　as　Re　increased.