Disclosed is a mounting structure in which an upper radiator of a vehicle is mounted on a chassis. The mounting structure includes: a frame installed right and left sides of an upper tank of a radiator; an insulator inserted on the frame, and having a groove for receiving a pin in its center; a mounting hole formed on a front end carrier positioned on an upper portion of the radiator; a pin inserted into the groove for receiving pin and the mounting hole, for fixing the upper portion of the radiator in the front end carrier. Therefore, the radiator is easily joined to a chassis.