Compared with the traditional geomagnetic observation method, the buried geomagnetic observation method has the advantage of small area, no surface buildings, simple construction and no restriction of farmland protection. It effectively avoids the difficulties of land acquisition and magnetic house construction, so it can be built in the protected area with excellent observation environment, which is conducive to the promotion of construction and the development of a large range of geomagnetic observation. Aiming at the problems existing in the current buried geomagnetic observation devices, a new prefabricated buried design scheme is proposed in this paper. The theoretical calculation and experimental verification of the observation device, such as insufficient heat preservation, improper waterproof treatment, low stability and short service period, are carried out from the aspects of material use, structural design, construction layout and warehouse insulation. The results show that the actual maximum daily temperature difference of the device is less than 0.2℃, and the theoretical annual temperature difference is less than 8℃, which is of simple construction, high stability, good waterproof performance and heat preservation.