Abstract: Such features as higher stability, quick operation, and convenient maintenance of the proton precession magnetometer in the use of geomagnetic total field measurement make it very suitable to be installed in dense network of geomagnetic observatories or survey sites for monitoring the seismo-magnetic phenomena. But some people propose that it is necessary to measure the geomagnetic component, especially the vertical, to monitor the seismo-magnetic phenomena.In this paper the effectiveness of the total field measurement in monitoring the seismo-magnetic phenomena is proved on the basis of the formula separating local anomaly origin into external and internal parts. It is shown that the range of anomaly of the total field, △F, can not be zero anywhere in the entire anomalous region and that it is comparable with the range of the component anomalies, △H or △Z. This makes it possible to monitor in seismic region the whole process of the seismo-magnetic phenomena, specially and temporally with a set of dense observatories or survey sites using PPM.