The invention relates to a photosynthetic hydrogen preparing device and a technology for preparing hydrogen. The photosynthetic hydrogen preparing device comprises a base, a reactor arranged on the base and a rotating mechanism which can enable the reactor to rotate, wherein the reactor comprises a roller body extending in the horizontal direction, a charging assembly arranged at one end of the roller body, a discharging assembly arranged at the other end of the roller body, a support shaft located at the central shaft of the roller body, a plurality of support strips of which one ends are connected with the support shaft and the other ends are connected with the inner wall of the roller body, a light source assembly and a heater; the light source assembly comprises a light source arrangedin the roller body, a triangular prism and a light source power arranged outside the roller body; a light reflecting coating is formed in the surface of the triangular prism; and the light source isdistributed on the support strips. The invention provides a roller type photosynthetic hydrogen preparing reactor which is simple in structure, convenient to operate, high in treatment efficacy, smallin floor space, short in time consumption, high in applicability, energy-saving and environment-friendly, and the amount of prepared hydrogen of feed liquid is increased.