It's important to dissipate the heat of modern electronic components. The influences of heat sinks with or without heat pipes and with or without fins are simulated under the condition of natural convection by the CFD software Fluent. Through the model based on the numerical study, temperature distribution maps at different kinds of heat sinks and different power are obtained and analyzed. Additionally, experimental results demonstrate the validity of the simulation analysis. It is shown that the heat sink with heat pipe and fins can satisfy the required working temperature of the germanium transistor, while the heat sink with fins but without heat pipe can satisfy the required working temperatures of the silicon tube and the electron tube, under the condition of natural convection.