Main chain chiral liquid crystal elastomers, with periodic nanostructures, are a kind of soft photonic crystals, including cholesteric liquid crystal elastomers and blue phase liquid crystal elastomers. They can not only reflect circularly polarized light selectively, but also dynamically adjust their structural color responding to changes in the environment, which could find wide applications in adaptive optics, bionic camouflage, information encryption, intelligent soft robots and so on. With the development of new material systems and advanced preparation techniques, researchers have explored various ways to design and synthesize chiral liquid crystal elastomers for emerging applications. Main-chain cholesteric liquid crystal elastomers are mainly prepared by parallel orientation, anisotropic deswelling, bar coating, and 3D printing. The parallel orientation method is a traditional method, which usually occurs within liquid crystal cells with planar-aligned alignment. Due to the interaction of liquid crystalline molecules with alignment coatings, helical nanostructures’ self-assembly can occur. The parallel orientation method has been used to design and develop photonic liquid crystal elastomers, 4D photonic actuators, inflating chiral nematic liquid crystalline elastomers with broadband and pixelated camouflage, chameleon skin-like cholesteric liquid crystal elastomers and other advanced functional materials. Based on the two-stage thiol-acrylate Michael addition and photopolymerization reaction, a facial and easily scalable method has been proposed to prepare uniformly colored large-area cholesteric liquid crystal elastomer films, which benefits from anisotropic deswelling. The gel formation from the Michael addition adheres strongly to the substrate, restricting the deswelling to take place only in the vertical direction and causing an in-plane orientation of the liquid crystal director. The resulted film with helical nanostructures shows a robust, rapid, and reversible mechanochromic response to strain, resulting in a broad color shift across the full visible spectrum. During the bar coating method, the precursor was applied to a bare substrate at a certain temperature via an applicator. Because of the shear forces during the bar coating process, the mesogenic molecules are able to align along with a common director, resulting in the formation of cholesteric liquid crystal elastomers with brilliant reflection color. The thickness of the film was controlled by changing the distance between the applicator and the substrate. This bar coating method has important significance for the application of advanced photonic crystal coatings. 3D printing is an emerging and advanced fabrication technique, and current 3D printing technologies for liquid crystal elastomers include direct ink writing and digital light processing. During the direct ink writing process of cholesteric liquid crystal elastomers, a viscous ink composed of uncrosslinked liquid crystal oligomers is often extruded from the printing nozzle. The shear force generated during the extrusion process causes the mesogens to spontaneously align along with the printing path, forming periodic helical nanostructures that selectively reflect circularly polarized light. Unlike cholesteric liquid crystal elastomers, blue phase liquid crystal elastomers are generally prepared through injecting chiral liquid crystal materials into liquid crystal cells, heating to isotropic phase, and then slowly cooling down. The liquid crystal precursors can self-assemble into a three-dimensional cubic lattice without the assistant of the surface alignment. The resulting blue phase liquid crystal elastomers have narrow photonic band gaps, which could enable functional implementations in nonlinear optics, lasing, spectral imaging and energy applications. In this review, different preparation methods of main-chain chiral liquid crystal elastomers are synthetically introduced. The state-of-the-art advancement and future perspective of main-chain chiral liquid crystal elastomers are discussed. It is expected that this review could shine new light on the development of advanced chiral liquid crystal elastomers and their emerging applications in diverse fields such as adaptive photonics, soft robotics, electronic skins and beyond.