Accurately obtaining the original information of an in-situ rock via coring is a significant guiding step for exploring and developing deep oil and gas resources. It is difficult for traditional coring technology and equipment to preserve the original information in deep rocks. This study develops a technology for in-situ substance-preserved (ISP), moisture-preserved (IMP), and light-preserved (ILP) coring. This technology stores the original information in real time by forming a solid sealing film on the in-situ sample during coring. This study designed the ISP-IMP-ILP-Coring process and tool. In addition, an ISP-IMP-ILP-Coring process simulation system was developed. The effects of temperature, pressure, and film thickness on the quality of the in-situ film were investigated by performing in-situ film-forming simulation experiments. A solid sealing film with a thickness of 2–3 mm can be formed; it completely covers the core sample and has uniform thickness. The film maintains good ISP-IMP-ILP properties and can protect the core sample in the in-situ environment steadily. This study verifies the feasibility of “film formation during coring” technology and provides strong support for the engineering application of ISP-IMP-ILP-Coring technology.