The disclosure provides a retainer which is configured to be mounted on and fix heat dissipation module onto chip platform. The retainer includes pressing portion, first and second latching portions. The first latching portion includes flat portion and flexible curved portion, the flexible curved portion is connected between the pressing portion and the flat portion, long side of the flat portion is substantially perpendicular to a long side of the pressing portion. The second latching portion is connected to the pressing portion. A long side of the second latching portion is substantially perpendicular to the long side of the pressing portion. The first portion and the second latching portion are configured to be detachably engaged at two opposite sides of the chip platform so as to deform the flexible curved portion and utilize the flexible curved portion to enhance a pressing force applied to the heat dissipation module.