A heat dissipating assembly of a heat dissipating device includes an integral formed plastic retaining seat; and a heat conductive tube. A part of one end of a heat conductive tube is embedded into the plastic retaining seat and another end of the heat conductive tube is connected to a heat dissipation device. In using, the heat conductive tube is placed above the heat source. Wherein heat dissipated from the heat source is transferred to the heat conductive tube and then to the heat dissipation device so as to be dissipating out; and thus the heat source has a stable working environment. The plastic retaining seat is used to replace the prior art metal seat, which is easily manufactured and is light. Thus the cost is low and the size thereof is compact. Moreover, few steps are necessary in manufacture and the cost in assembly is low.