This study was executed by dust explosion experiment of terephthalic acid which was widely used for various purposes of food packing material and film etc. and the demand was rapidly increasing. The particle size and concentration of dust affected the minimum ignition energy largely and the lean concentration and the minimum ignition energy in the range of this study were obtained 50$g/m^3$ and 19mJ respectively. Minimum ignition energy was shown at the 4 and 5mm gap distance of discharge electrode, and when the gap distance was below 2mm the explosion could not generated although the sufficient energy was given. It was also found that the ignition energy decreased linearly with the decreasing of dust mean particle size.