Abstract: A theoretical formula of power compensation DSC curve was derived from the law of energy conservation and heat transfer. The DSC melting curve of pure indium was studied as an example. It was illustrated that the heating trace of pure indium consists of three parts, which include 〝before melting〞, 〝melting〞 and 〝after melting〞process corresponding to the three components of DSC theoretical formula, respectively. DSC curve analysis disclosed that melting temperature corresponds to the onset temperature of 〝melting〞curve. 〝After melting〞 curve decays exponentially. The larger the value of thermal time constant is, the longer the time of 〝after melting〞 curve experiences. Melting enthalpy equals to the area above base line and beneath 〝melting〞 and 〝after melting〞curve. The theoretical basis for thermal resistance (R) measurement and the effect of R on the DSC curve shape were illustrated. A simulated DSC curve of a multi-component system was produced to explain the origin of the characteristics of DSC melting curve of polymers.