Fluxgate magnetometer LEMI-025 was specially developed for the super stable 3-component measurements of Earth magnetic field induction and their variations in accordance with new 1-second INTERMAGNET standard. In order to realize this design major attention was paid to frequency response and sampling synchronization accuracy as well as thermal and temporal stability and noise level for magnetic channels. In order to fulfil such mutually contradictory requirements as speed of response and deep suppression of industrial noise the specific combination of analogue and digital filters was realized in this instrument. The magnetic sensor of flux-gate type, which mainly determines magnetometer stability and noise level, was manufactured using well-proved technology on the base of marble and quartz combination. The rotating sensor support has two bubble levels and levelling facilities to provide proper orientation of its components at the selected place. The instrument is intended for operation in the geomagnetic observatory conditions and is both accumulating data into a removable Compact flash memory card up to 2 GB and/or transmitting to the external PC for storing of the acquired data.