Blue phase liquid crystal elastomer (BPE) is a functional material integrating three-dimensional photonic crystal structure and rubber soft elasticity and has a wide application prospect in the field of liquid crystal photonics. However, the novel preparation method and elastic properties of BPEs need to be further investigated. On the basis of in-situ photopolymerization, BPE films with different mercaptan (EDDET) contents were prepared by introducing the click chemical reaction between EDDET and acrylate. The influence of EDDET content and UV curing on the lattice structure, thermal stability and optical properties of BP were systematically studied, in ddiion, the elastic properties and stress color change properties of BPE prepared with different EDDET concent were measured. The experimental results show that EDDET could effectively fill the disclination network of BP. With the increase of EDDET content, the thermal stability of BP was increased by 5 times. The UV light curing process would induce BP lattice deformation. As the EDDET content increased, the fracture length of BPE film was increased by 7 times, and the stress decreases by about 52 times with the same change of the Bragg reflection peak of BP. We believe that the BPE films prepared by this method has a wide application in the fields of intelligent bionics, sensing, anti-counterfeiting, lasing and so on.