earthquake include phenomena that occur before the earthquake and Investigating their changes can lead to short-term earthquake prediction. In this study, by processing geomagnetic data of three stations, anomalies in the data were evaluated before the earthquake. By frequently drawing data for every 24 hours during the two months (one month before and one month after the earthquake) July 20, 2017 Greece whit magnitude 6.6, the characteristic curves were plotted for all three components of the magnetic field. The resulted characteristic curve which is obtained by averaging the uncertainty band composed of the data, is removed from the original record by simple subtraction. The anomalies can be seen better after implementing this method. The results show that 4 days before the earthquake, the magnetic field fluctuations have shown a significant increase in amplitude