Embodiments of the present disclosure relate to a fixing device for a double-sided heat sink and an associated heat dissipating system. There is exemplarily provided a fixing device for mounting the double-sided heat sink on a carrier. The fixing device comprises: a first holder including a first cylindrically-shaped rod, wherein the first cylindrically-shaped rod can pass through a first cooling portion of the double-sided heat sink and a mounting hole of the carrier to fix the first cooling portion to a first side of the carrier, and the first cylindrically-shaped rod comprises a through-hole extending along a longitudinal direction; and a second holder including a second cylindrically-shaped rod, wherein the second cylindrically-shaped rod can pass through a mounting hole of a second cooling portion of the double-sided heat sink and the through-hole of the first holder, such that the second holder is coupled with the first holder to fix the second cooling portion to a second side of the carrier opposite to the first side.