Heat sink of central processor of computer system

The utility model relates to a heat sink of the central processor of a computer system, comprising heat conducting fins, a cover plate and a fan. The heat conducting fins are U-shaped and superposed on the top surface of a central processing unit. The cover plate is fixedly arranged on the top surface of the heat conducting fins; an air duct whose circumference is closed is formed between the cover plate and the heat conducting fins. An air inlet and an air outlet are respectively formed on both sides of the air duct. The fan is fixedly arranged on the lateral sideof the air inlet of the air duct. The heat which is produced by the central processing unit is absorbed by using the heat conducting fins. When the cold air which is sucked by the fan enters the air duct, the cold air is exhausted outside a host computer from the air outlet. The utility model can prevent heat flow from circulating in a machine body.