A gasification apparatus for solid fuel, comprising a furnace shell system, a gasification chamber system, and a syngas cooling and purifying system, the furnace shell system includes a furnace body of cylindrical structure and a cone-shaped disk, wherein a feeding inlet is on the top of the furnace body, a slag outlet is at the bottom of the furnace body and a syngas outlet is provided in the middle of the furnace body, the furnace body is divided into an upper furnace body and a lower furnace body by the cone-shaped disk, the upper furnace body comprises a gasification chamber which is located in the upper furnace body, and the lower furnace body comprises a syngas cooling and purifying chamber which is located in the lower furnace body, the gasification chamber has a water-cooling wall structure, a layer of fire-resistant material is evenly coated on the inner side of the water-cooling wall, and an annular cavity is between the water-cooling wall of gasification chamber and the furnace body, wherein a purifying system including a syngas-cooling device is provided in the syngas-cooling chamber, the syngas-cooling device is connected with the cone-shaped disk located at the bottom of the gasification chamber, and the purifying system further includes a vertical pipe, characterized in that: the purifying system further includes a gas uniform distribution device, a defoaming device and a dewatering and deashing device, the vertical pipe is connected with the syngas-cooling device by means of an outlet flange located in the middle of the bottom of the gasification chamber, wherein the connection is located in the middle of the bottom of the gasification chamber, a trumpet-shaped gas uniform distribution device is connected with the lower portion of the vertical pipe via a smooth transition, a baffle device is arranged above the gas uniform distribution device, a defoaming device is arranged 100-800 mm above the baffle device, and a dewatering and deashing device is arranged 100-800 mm above the defoaming plate at the uppermost layer of the defoaming device, that the gasification apparatus further comprises a flame observing system which is put into use only at the start of the device operation, the flame observing system bottom-up sequentially includes an observing tube, a cut-off valve, a transparent material layer and an industrial camera, an inlet flange for protective gas is connected with the side wall of the observing tube which is embedded in the fire-resistant material on the inner side of the inlet water-cooling wall through a furnace cover at the feeding inlet located at the top of the furnace body, an observing hole is preserved at the lower portion of the observing tube to communicate with the gasification chamber, the protective gas is flowed into the observing tube from the inlet flange for the protective gas, and the industrial camera observes the ignition conditions in the gasification chamber by means of the observing tube through transparent material layer and passes the obtained information back to a control room of the apparatus, and that the gasification apparatus further comprises a temperature monitoring system comprising several temperature detecting devices in the furnace arranged in circumferential direction at different heights of the body water-cooling wall, and the temperature detecting devices in the furnace protrude from the fire-resistant material of the water-cooling wall by 0-15 mm so as to monitor the temperature in the furnace in real-time.