Utilizing coal waste byproducts formed during mine development or use is important in solving environmental problems and recycling of waste materials. In this study, specimens prepared by mixing coal waste of 10, 20, 30, 40, and 50% into clay brick have been investigated in terms of water absorption and compressive strength according to coal waste amounts and calcination temperature. As coal waste content increased water absorption increased and compressive strength decreased. When up to 30% coal waste was mixed into clay at 1300 degrees C, specimens satisfied 1(st)-class brick of Korea Standard requirements (water absorption 10%>, compressive strength 210 kgf/cm(2)<).