The invention discloses a non-magnetic fully-sealed triaxial fluxgate magnetometer. The magnetometer comprises a casing, a fully-sealed cavity, a measuring coil and a magnetic core, and a plurality of welding needles are sintered on the fully-sealed cavity through glass. Meanwhile, the invention further discloses an installation method for the magnetometer. Compared with the prior art, non-magnetic alloy and seal glass with the same expansion coefficient and the non-magnetic fully-sealed glass sealing technology are researched, and in this way, in the wide temperature range, the triaxial fluxgate magnetometer is in the zero stress state, can conduct simultaneous precision measurement on three components of a magnetic field at the same point in space, and has good repeatability of temperature modeling.