Zinc oxide (ZnO) is a natural semiconductor with a theoretical bandgap of 3.37eV. It has become one of the most popular materials in the application of ultraviolet photodetectors in recent years. However, due to the intrinsic defects of ZnO, the directly prepared ZnO ultraviolet photodetectors always display low responsivity, high dark current and slow response speed. To obtain the better performance of ultraviolet photodetectors, various feasible methods for performance improvement and modification are proposed. In this paper, the typical methods to improve the performance of ZnO ultraviolet photodetectors are reviewed from the three aspects of element doping, surface modification and hetero-structure construction, the existing problems of these methods are pointed out and the potential development of high-performance ultraviolet photodetectors in the future is prospected.