Liquid crystalline polymers with tunable structures on the scale of visible wavelength are important in optical technology due to their enhanced mechanical stability, processability, and structural integrity. Herein, we report a series of cholesteric liquid crystalline (CLC) polyethers with a widely tunable pitch length and a broad CLC phase window through a bottom-up structural design. The well-defined multicomponent polyethers were successfully synthesized by utilizing monomer-activated anionic ring-opening polymerization. Through adjustment of the composition of chiral cholesteryl (Ch) and photochromic azobenzene (Az) mesogenic moieties, rich phase behaviors have been discovered, and a phase boundary diagram was constructed consequently, wherein cholesteric helical superstructures in a broad composition range and temperature window straight down to the glassy state at room temperature were achieved. Particularly, the planar oriented helical superstructures can exhibit widely tunable and switchable reflections over the entire visible range across red, green, and blue colors through temperature and light control, which are closely related to the extraordinary flexibility of the polyether backbone. Their thermo-light dual-responsive properties provide an alternative opportunity to fabricate smart and switchable polymeric LC materials for optical applications.