In order to obtain deformation parameters in the south segment of Longmenshan fault zone，Euler datum transformation and the least square collocation for data interpolation and smoothing are used to process GPS displacement time series data in the south segment of Longmenshan fault zone，and the rigid and elastic-plastic block motion model is used to calculate the strain parameters in each subarea． Conjoint analysis of displacement， velocity of each station and strain parameters of each subarea reveals that the influence of the Wenchuan earthquake on the south segment of Longmenshan fault zone increases from southeast to northwest，causing a highest deformation rate 6 times the background value and heightening the influence of the hidden faults on the difference of the earth surface along its two sides，which leads to the seismic risk of the southern segment increasing from north to south． The comparison of seismic risk among subareas based on the tectonic and seismicity background indicates that the most dangerous area is on the southeast of Longmenshan faults，and the background strain accumulation and the promoting effect of the Wenchuan earthquake advanced the occurrence of Lushan earthquake and the sinistral strike-slip on the rupture plane． The Wenchuan earthquake also caused a slight two-year long continuous strain release in the south segment of Xianshuihe fault，but the influence is far less than the effect of the compressive strain caused by the Sichuan-Yunnan block．