The observation data of satellite CloudSat are used to analyze the mechanisms of freezing rain in Guizhou Province. The results show that, for the freezing rain under icephased mechanism, reflectivity of cloud profile radar, ice water content and temperature profile of CloudSat data could describe the process of icephased particles melting into liquid clearly. Bright bands of reflectivity at the 0℃ layer of cloud profile radar are the direct reflection of the melting process, and ice water content data could represent the melting process in melting layer as well. For the freezing rain under the supercooled warm rain mechanism, CloudSat data could depict the falling process of precipitation particles kept in the supercooled liquid in environment of temperature below 0℃ vertically. This research proves that the Guizhou freezing rain has warm rain mechanism with melting layer based on observation of cloudphysics. With the existence of temperature inversion in vertical temperature profile, precipitation particles exist in the liquid state in melting layer but remain supercooled in environment of temperature below 0℃. The supercooled liquid precipitation particles could be heated when falling into melting layer, getting frosted into supercooled droplets in freezing layer below, colliding with surface objects and forming freezing rain with temperature below 0℃ at last. Thus, melting layer could not be used to distinguish the formation mechanism of freezing rain.