Using GPS observation data for the middle segment of the Fenwei seismic zone during the time period of 1996～2001, the velocity field of crustal movement is calculated. Thus, the vectors of relative horizontal movement between measuring points in the region are also obtained. Adopting a deformation model of homogeneous elastic body, the principal strain rate parameters of deformation units are calculated. A method is introduced to calculate the rate of seismic moment accumulation due to crustal deformation. The problems of using this rate to analyze the tendency of seismicity in the zone, and to estimate the recurrence interval of large earthquakes in the potential seismic source areas(PSSA) are discussed. The results show that the rate of seismic moment accumulation in the middle segment of the Fenwei zone is 4.22×10 17 Nm/a, which is much higher than the average release rate of seismic moment in the current activity period. This means that the belt is now in a stage of seismic strain accumulation and that the seismicity would become stronger in the future than now. The results of estimation of the recurrence interval of large earthquakes in the Dingxiang and Huozhou PSSA are close to the results obtained from studying active faults. This implies that the use of the proposed estimation method is worthy of further investigation. In particular, it is of greater practical significance for those regions that have shorter history of earthquake records or lower degree of active structure study. Using GPS observation data for the middle segment of the Fenwei seismic zone during the time period of 1996 ~ 2001, the vectors of relative horizontal movement between measuring points in the region are also. Adopting a deformation model of homogeneous elastic body, the principal strain rate of deformation units are calculated. A method is introduced to calculate the rate of seismic moment accumulation due to crustal deformation. The problems of using this rate to analyze the tendency of seismicity in the zone, and to estimate the recurrence interval of large earthquakes in the potential seismic source areas (PSSA) are discussed. The results show that the rate of seismic moment accumulation in the middle segment of the Fenwei zone is 4.22 × 10 17 Nm / a, which is much higher than the average release rate of seismic moment in the current activity period. This means that the belt is now in a stage of seismic stra in accumulation and that the seismicity will become stronger in the future than now. The results of estimation of the recurrence interval of large earthquakes in the Dingxiang and Huozhou PSSA are close to the results obtained from studying active faults. This implies that the use of the the proposed estimation method is worthy of further investigation. In particular, it is of greater practical significance for those regions that have shorter history of earthquake records or lower degree of active structure study.