Various coals from many countries around the world have been used for pulverized coal boiler in power plants in Korea. In this study, the gasification reactivities of various coal chars with $CO_2$ were investigated. Carbon conversion was measured using a real time gas analyzer with NDIR CO/$CO_2$ sensor. In a lab scale furnace, each coal sample was devolatilized at $950^{circ}C$ in nitrogen atmosphere and became coal char and then further heated up to reach to a desired temperature. Each char was then gasified with $CO_2$ under isothermal conditions. The reactivities of coal chars were investigated at different temperatures. The shrinking core model (SCM) and volume reaction model(VRM) were used to interpret the experiment data. It was found that the SCM and VRM could describe well the experimental results within the carbon conversion of 0-0.98. The gasification rates for various coals were very different. The gasification rate for any coal increased as the volatile matter content increased.