A hydropyrolysis and gasification coupling method for a powdered coal fluidized bed is disclosed. According to the method, in a first step, a heat source of a hydropyrolysis furnace of the powdered coal fluidized bed is synthesis gas from a gasification furnace, a hydrogen source comprises following two parts: (1) hydrogen in the synthesis gas and (2) hydrogen prepared by purification of gas produced in a system; in a second step, most of solid semicoke produced by hydropyrolysis is directly fed into a semicoke hopper through a coke guiding pipe, and a small part of the semicoke with a small particle size is fed into a cyclone separator together with pyrolysis gas, the semicoke enters the semicoke hopper after separation by the cyclone separator; and in a third step, a raw material of the gasification furnace is the semicoke prepared by the hydropyrolysis, the semicoke and a gasifying agent are subjected to a gasification reaction according to a certain ratio in a gasification reactor to produce high-temperature synthesis gas, and the high-temperature synthesis gas is adopted as the heat source and the hydrogen source of the hydropyrolysis furnace of the powdered coal fluidized bed. Quality of tar obtained by hydropyrolysis of coal is good. The content of obtained effective gas is high.