The invention discloses a gasifier, which is provided with, from bottom to top, a secondary gasifier and a first gasifier in superposing arrangement. The first gasifier is provided with a feed inlet and a carrier gas port; the external vertical direction of the first gasifier is provided with a motor; the output shaft of the motor extends into the first gasifier is provided with a plurality of tray layers; the inner wall of the first gasifier is provided with a plurality of heating element groups; a passage between the first gasifier and the second gasifier is provided with a one-way conveyor belt; the side surface of the second gasifier is in communication with a cyclone dust collector; and a medium inlet is arranged on the second gasifier. The invention also discloses a household refuse harmless gasification energy process; the gas produced by the invention has high calorific value achieving 4080Kcal/Nm<3>; the gas produce production does not produce tar; and the household refuse does not need classification treatment and can be directly sent into the process cycle, so as to dramatically reduce the amount of equipment, labor costs and energy consumption.