The present invention discloses an exhaust gas inlet structure of an exhaust gas recirculation (EGR) Cooler which includes a water shell, a gas inlet pipe, a bellow, an insulated pipe, an inlet chamber, a pre-cooling water chamber and a main board. The water shell is equipped with a water inlet pipe. Its main feature is the insulated pipe is placed within the bellow and connected with the gas inlet pipe at one end while the other end is suspended. The large-bore end of the inlet chamber is connected with the main board to form a gas inlet cavity while leaving a space to form a coolant channel between the joining part and the water shell. An external surface of a middle pipe body connects to the bellow to form a pre-cooling cavity connected to the coolant channel. The advantages of the present invention are as follow: newly-added pre-cooling water chamber reduces the wall temperature of the main board and the inlet chamber; newly-added supporting in the middle part of the insulated pipe improves the vibration-proof function of the insulated pipe; the special structure of the inlet chamber increases the ability of the axial displacement compensation. The above-mentioned improvement of the present invention significantly improves the reliability of the EGR cooler.