Disclosed are a 4H-SiC ultraviolet photoelectric detector with a spherical crown structure, and a preparation method. The ultraviolet photoelectric detector adopts a p-i-n structure; an N type bufferlayer and an i type absorption layer are grown on a highly-doped four-degree-off-axis double parabolic N+ type 4H-SiC substrate in sequence; an arc-shaped inclined table surface is formed on the i type absorption layer to form a spherical crown-shaped i type absorption layer surface; by adopting an injection and high-temperature annealing activation process, a P+ layer is formed on the upper surface of the spherical crown-shaped i type absorption layer; next, through a thermal oxidization method, a silicon dioxide passivation layer is grown on the surface of the P+ layer; through a photoetching process, an ICP etching process and a stripping process, a P type annular electrode window is etched in the silicon dioxide passivation layer of the P+ layer, and a P type electrode is formed by adopting a magnetron sputtering process; and the highly-doped four-degree-off-axis double parabolic N+ type 4H-SiC substrate on the back surface is etched, and an N type electrode is formed by adopting amagnetron sputtering process, so as to obtain the 4H-SiC ultraviolet photoelectric detector with the spherical crown structure.