The invention discloses a steam generator applicable to the variable-gravity environment. The steam generator comprises a shell, a liquid inlet located in one end of the shell, and an air outlet located in the other end of the shell. A heating device is arranged in the shell and is annularly arranged in the shell; a porous foam metal capillary core is arranged in the heating device; and channels for steam to pass through are arranged between the heating device and the porous foam metal capillary cores, and communicate with an air outlet. According to the steam generator applicable to the variable-gravity environment provided by the invention, the function of capillary force of porous foam metal is utilized to extract liquid, and can overcome the influence of bubble retardation in a micro-gravity environment, so that the liquid is dispersed into a cavity; with high thermal conductivity and a high specific surface area of the foam metal, the gasification core number and the heat transfer area of bubbles are increased, the heat exchange performance is enhanced, and the aims of simple system, low cost, safety, reliability, efficient heat exchange and fluid distribution are achieved.