The spatial distributions and seasonal variations of the main fronts in GIN seas are analyzed by grid data of monthly mean of temperature and salinity. The suitable application method for monthly data in frontal study is discussed. As the fronts often move or swing, the front information in monthly data has been blurred and the fronts obtained by monthly mean temperature and salinity sometimes show  interrupted front and multi-front phenomena. However, the blurry fronts are just the averaged status of fronts, which can only be revealed by monthly data. The fronts show significant diversity in their characteristics and seasonal variations. The East Greenland Polar Front (EGPF) is mainly a salinity front, being evident and continuous in summer and weak and interrupted in winter. The EGPF is also a temperature front in summer. The obvious temperature gradient and uninterrupted shape appears  in September, being attributed to the maximum temperature difference between the East Greenland Current and the return currents at that time, which keeps the location of EGPF relatively stationary. The Arctic Front (AF) has a seasonally spatial variation with "dumbbell" shape—The seasonal displacement near the northern and southern parts of the front is much larger than that in the middle part, showing the larger swinging amplitude there. AF near the Mohn Ridge was addressed as a no-motion part, however, AF by this study is revealed to move northwestward in winter because the flux of Norwegian Current reaches the maximum then and induces the broadest width of the current near the Mohn Ridge area. A special characteristic of the Iceland-Faroe Front is that the interface of the front appears more southward and stronger in deep part, which is caused by the overflow above the ridge.