A temperature model of the phase change memory (PCM) cell having Ge2Sb2Te5 (GST) layer has been proposed and demonstrated based on a thermal physical model and electrical characteristics. Calculating the radius of PCM cell with different reset voltage pulse based on the voltage-current curves by the temperature equation, the crystalline fraction can be got. It is found that the crystalline fraction and temperature of active region increase with the reset voltage pulse increasing. The experimental results are consistent with the simulation results. (C) 2010 Elsevier Ltd. All rights reserved.