For large aperture and high-resolution space optical cameras, the focusing requirements caused by different resolution requirements, or the requirements for the segmented primary mirror for deployable telescopes or on-orbit assembly space telescopes, the micro- or nano-metric multi degree of freedom adjusting of the primary mirror or the segment mirror is one of the inevitable development trends of the active optical system. According to the different degrees of freedom involved in the primary mirror adjustment, the micro- or nano-metric multi degree of freedom adjusting displacement scaling mechanisms of the monolithic and segmented primary mirror are studied. The development history and structural characteristics of multi degree of freedom adjusting displacement scaling mechanisms including rigid lever type, gear deceleration type, hydraulic mechanism type and compliant hinge type, as well as their research status and application fields, are introduced. The performance characteristics and applications of various displacement scaling mechanisms are analyzed and compared. Finally, according to the application requirements of space telescopes in the future, the development trend of multi degree of freedom (DOF) adjusting displacement scaling mechanism for segmented primary mirror is proposed.