Abstract:On the basis of the observations from Tianjin GPS site during 1995-1999, 1999-2004 and 2004-2009, the principal strain rate and the difference of strain rate of fault zone were calculated for different blocks. The results show that the principal compressive stress direction of the overall Tianjin was the NW direction in the first two periods, the NEE direction in the last period, which is revealed by the direction of principal strain. The principal compressive stress direction of secondary small block changes considerably. Some of faults in block boundaries have become strain gradient zone, while the others are not obvious. The differences between the differential strain rate of fault zone are significant in different periods. Seismic activity has a certain relationship with high strain zone, strain gradient zone, and the zone with higher differential strain rate of fault zone.