The invention relates to a self-protection device and method and in particular relates to a gasifier power failure self-protection device and method, aiming to solve the problem that shut-down accidents are easily caused by power failure or water pump failure because existing coal gasification devices adopt forced water circulation modes. The device is characterized in that the upper end of a water wall tube is connected with an upper header; the upper header is connected with a gasifier steam drum by a gasifier steam and water guide tube; the two ends of a downcomer bypass are connected with a downcomer; a gasifier forced circulation water pump is arranged between the upper and lower ends of the downcomer bypass; a steam circulating pump is installed on the downcomer bypass and is connected with a gasifier steam drum steam outflow tube by a steam inlet tube; the gasifier steam drum steam outflow tube is connected with the gasifier steam drum; a gasifier steam drum feed tube is connected with a water inlet of the gasifier steam drum; and a synthesis gas channel is inserted in the lower part of a gasifier. The device and the method are used in the field of coal gasification.