A liquid storage device for a propellant tank in a spacecraft includes a gas-guide tube, a cover plate, a housing, blades, a supporting column, a base, a passage-window pressing plate, a passage-window mesh piece, a liquid-storage-device mesh piece, a fixing block, and a pressing plate for the liquid-storage-device mesh piece. The blades are uniformly distributed on and fixed to the support column in a radial direction to form an integral structure, and the integral structure is mounted on and fixed to a circular partition plate in the base. The liquid-storage-device mesh piece is pressed on the circular partition plate in the base by the pressing plate for the liquid-storage-device mesh piece and then is fixed. The passage-window mesh piece is pressed on the outer side of a cylinder wall of the base by the passage-window pressing plate and then is fixed.