The G-856 proton precession magnetometer is characterized by high accuracy,intelligence and combined application with computer.It is suitable for seismomagnetic precursor observation and earthquake prediction research.Main property of the magnetometer and results of its property test are introduced.The optimum seismomagnetic observation should be to mainly observe geomagnetic total intensity with proton magnetometer and combine to observe geomagnetic three components and geomagnetic shortperiod variations.