In this study, the effect of microwave treatment on grindability of low rank Turkish coal has been investigated. Coal samples (-9.52 + 3.18 mm) was treated by microwave at a frequency of 2.45 GHz with different residence time (15-180 sec). In order to determine the grinding resistance of lignite samples treated by microwave oven, the impact strength index test was applied for each treated and untreated sample and compared with each other. Experimental results have shown that significant increases in grindability without damaging the coal structure were achieved when the coal samples were exposed to microwave radiation. The impact strength index of samples decreased up to 265%.