The invention belongs to the technical field of black fungus cultivation, and particularly relates to energy grass serving as a cultivation material for black fungus and a preparation device thereof.For conventional black fungus cultivation, wood dust and cottonseed husks are main raw materials; and forest resources are used up because of current annual large-area cultivation, and the cost is continuously increased, which brings a problem of extremely high restriction to the conventional black fungus cultivation. The technical scheme of the invention is to take the energy grass as a main leftover for the black fungus cultivation. Furthermore, the invention further provides a device for preparing an energy grass cultivation material for the black fungus. The device comprises a material feeding conveying belt I and a material feeding conveying belt II; a straw chopper for chopping the energy grass is arranged between the material feeding conveying belt I and the material feeding conveying belt II; a turnover type weighing table is arranged at the tail end of the material feeding conveying belt II; a material collection hopper is arranged below the turnover type weighing table; the material collection hopper is connected with a material mixing bin through a material conveying pipe; a heating bin is connected below the material mixing bin; a material outlet is formed below the heating bin. The energy grass is applicable to black fungus cultivation.