In double-helix point spread function (DH-PSF) engineering, the PSF of the conventional imaging system is transformed into DH-PSF using a regulation of pupil surface wavefront phase of imaging system to realize large-depth, high-precision nanoscale three-dimensional (3D) imaging. The DH-PSF is widely applied in life-science and material-science research, industrial detection, and other fields. In this study, the basic principle of the DH-PSF and the design and application methods of the DH phase mask are described in detail. Based on these, the applications of the DH-PSF to depth estimation, nanoscale 3D single-particle tracking, super-resolution fluorescence microscopy, and laser scanning fluorescence microscopy are introduced. The advantages of the DH-PSF technology in these application examples are emphasized, providing a useful reference for research in related fields. Finally, the prospects of the development direction of the DH-PSF technology and its application are discussed.