Abstract: In view of the difficulty in maintaining in-situ temperature and pressure during sampling of deepwater natural gas hydrates, based on the geometric principle of the Steinmetz solid, materials resistant to high pressure, low temperature, seawater corrosion, and fatigue and with a long service life were selected. An in-situ self-triggering pressure preservation controller for marine deep water was developed to achieve stable sample pressure during the sampling process of deepwater hydrates. Based on the fundamental principles of heat transfer, a variety of active and passive thermal insulation technologies were developed. By using a self-developed temperature control system and coupling three thermal insulation schemes, namely semiconductor refrigeration, phase change-based latent heat energy storage, and hollow microsphere composite materials, a new type of composite thermal insulation technology was formed, which met the thermal insulation requirements of samples during the sampling process of deepwater hydrates. Based on the research results of key tools and technologies for thermal insulation and pressure preservation sampling, a penetrating in-situ thermal insulation and pressure preservation sampler for deepwater natural gas hydrates was developed. Two sea trial operations were completed using manned deep-sea submersibles, and samples of deepwater sediments (natural gas hydrates) maintaining in-situ temperature and pressure were successfully obtained in both cases. The research result provides key technical support for the safe and efficient development of deepwater natural gas hydrates. It will also strongly promote scientific research and engineering practice in the field of in-situ thermal insulation and pressure preservation in deep water.