The invention relates to a device for solidifying fly ash. The device comprises a power transmission system, an electric heating system, a mud sheet roll forming system used for forming a fly ash liquid mixture and an electromechanical control system, wherein the power transmission system is composed of a water-ash mixed pug placing barrel, a pug mixing conveying pump assembly and a pug conveyingspraying pipe which are connected through a pipeline, the electric heating system is composed of a transmission segment, a transmission power rotating wheel, a closed shell and a forming electric heating plate which are mechanically connected, the mud sheet roll forming system is composed of a slitting piece, a rolling forming roller control assembly, a screening channel, a mud sheet roll formingassembly, a conical end, a movable adjusting piece, ash solid block separation equipment and ash solid block output equipment which are mechanically connected, and the electromechanical control systemis composed of a driving unit, a transmission power system, a rotation sensing device, an output transmission piece, an input transmission piece, a power connecting rod, a feedback output power rod and a mud sheet roll forming movable assembly which are mechanically connected. The invention further discloses a control system and a control method of the device for solidifying the fly ash.