Abstract: Based on the early experimental investigation,further numerical analysis of fluid flow and heat transfer in micro pin fin heat sink are discussed in this paper by utilizing the FLUENT,a commercial software.The results indicate that the turbulence model of RNG k-ε is more suitable for present experiment condition than other models.The streamline in the micro pin fins is very flexuous.Along the streamline,the pressure of the fluid decreases,while the fluid temperature increases.Vortexes with different sizes,in which pressure keeps constant and temperature fluctuates sharply,are found in the tail part of the pin fins.The heat transfer coefficient of fins reduces following the direction of flow,however,the scope decreases gradually too,and reaches a minimum at some points.The difference of heat transfer coefficient between face and back of the fins reduces as the progress of flow.