The invention discloses a method and apparatus for preparing coal water slurry. A coal-water slurry preparation apparatus includes the following parts: a pretreatment device, which is used for receiving raw coal and a microwave absorber, and for mixing the microwave absorber and the raw coal, wherein the microwave absorber comprises at least one of fine slag and carbon black; a microwave generating device, which is used for treating a mixture of the microwave absorber and the raw coal from the treatment device by microwave; and a pulping machine, which is used for preparing coal water slurry by using the microwave-treated mixture. The invention also provides a preparation method of the coal water slurry.