||Non-volatile memory (NVM) plays an important role in the market of consumer electronics. NVM are used as a storage medium for portable devices such as mp3 player and PDA. Dominating the NVM market in the past, flash memory has encountered many technical barriers in scaling beyond sub-50nm regime. Phase change memory (PCM) has become the next generation NVM to replace flash memory. PCM offers many advantages compared with flash memory, including excellent scalability, fast read/write speed and low power consumption. Most of the researches concerning PCM are focusing on its physical properties such as material properties and PCM structure. However, a PCM model suitable for circuit level simulation is not yet proposed. In this thesis, a physical model that calculates both the crystalline and amorphous state resistance of the PCM according to the PCM structure and dimension is built using resistor network method. The result of the model is compared and verified with the simulation result of device simulator. A PCM SPICE model for circuit simulation is developed and implemented in Verilog-A platform. The IV characteristic of the PCM cell at different states and programming can be correctly simulated by the model. Model for high level simulation such as multi-state PCM and date retention is also discussed. The model has also been calibrated by comparing with the experimental date reported in the literature.