The purpose of this research is to prepare ABS/MMT composites in various MMT with 1.5, 3 and 4.5 wt%. We use kneader to melt the products, and use injection molding to obtain the specimen. The composites thermal properties were measured. The experimental results show that the increase of MMT content will increase heat distortion temperature. The increase of MMT content will no significant change thermal conductivity, decomposition temperature and melting temperature. However, the adding a little MMT content in composites which will enhance the thermal properties.