The horizontal peak ground acceleration(PGA)distribution in an earthquake is a very important parameter and can be used as a reference for the determination of seismic intensity.In Minxian-Zhangxian MS6.6 earthquake disaster region,there is only Minxian seismostation in intensityⅦregion got the seismic records and in intensity Ⅷ region there is no seismic record.During site investigation,a kind of brick doorpost was noticed in Lalu village in Hetuo town,meizoseismal area.The doorpost with iron door broke in the earthquake and the doorpost without iron door kept in good condition,which can be used to estimate the PGA in this area.Based on the field investigation,the destruction features in meizoseismal area of the Minxian-Zhangxian MS6.6Earthquake are sketched and the damage to the brick doorpost with iron door in earthquake are described and analysed.The seismic intensityⅧregion is about 706km2 and the most serious damage area include Yongguang,Yongxing and Lalu villages,most of them located in the high half slope covered by thick loess.According to the characteristics of the doorpost and its break,the earthquake horizontal PGA was estimated by mechanics analysis theory using a simplified strut-node model,which can be used as a reference for seismic intensity division and post-disaster reconstruction design.The results show that the earthquake horizontal PGA of Lalu village in Hetuo town,meizoseismal area,is up to 5.1~5.4m/s2,namely 0.52~0.55g,which is much greater than the reference value of eight-degree region in the Chinese Earthquake Intensity Scale.Judging by the related study about the influence of local topography on ground motion in mountain region of southern Gansu province and the seismic records observed on Shangcheng platform in Wenxian during Wenchuan MS8.0earthquake,the high PGA may be caused by the amplification effects of both high mountain slope and thick loess in study area.Compared with the PGA value of seismic record by seismostation in Minxian-Zhangxian MS6.6earthquake and Lushan MS7.0earthquake,the PGA value is usually much higher than the reference value in the Chinese Earthquake Intensity Scale of the same intensity region.Therefore,these two effects should be considered for the post-disaster reconstruction and seismic fortification in the future and the fortification criterion should be increased for villages in high half slope area.