Large　landslides　often　cause　catastrophic　life　losses　and　infrastructure　damage.　Identification　of　the　driving　forces　of　large　ancient　landslides　is　of　utmost　importance　for　the　understanding　of　geohazard　assessment　and　regional　geomorphologic　evolution　and　for　the　understanding　of　regional　paleoclimate　and　paleoseismology.　Through　field　geological　survey,　multi-temporal　satellite　image　interpretation,　sedimentological　observation,　and　static　and　dynamic　numerical　simulation,　the　paper　studied　the　geo-environments　and　deposit　succession　of　the　Hongshiyan　paleolandslide　(HSYPL),　over　against　the　Hongshiyan　landslide　(HSYL)　triggered　by　the　2014　Ludian　M-S　(surface　wave　magnitude)　6.5　earthquake.　The　study　reveals　that　(1)　the　HSYPL　and　HSYL　are　symmetrically　distributed　on　the　opposite　banks　of　the　Niulan　River　and　on　the　opposite　wings　of　a　vertical　anticline　plunging　west.　Both　landslides　involved　an　anti-dip　slope　structure　of　upper　hard　rock　while　lower　soft　rock.　(2)　Two　phases　of　deposit　succession　in　the　paleolandslide　accumulations　were　recognized　from　their　surficial　appearances,　planar　distribution,　spatial　superimposition　relationship,　permeability　test,　and　borehole　survey.　(3)　The　deposit　did　not　result　from　one　single　paleolandslide　event　but　two　long-interval　individual　events,　i.e.,　penultimate　landslide　(PL)　and　last　landslide　(LL),　whose　source　volumes　were　estimated　to　be　similar　to　11.8　Mm(3)　and　similar　to　113.5　Mm(3),　respectively.　(4)　These　two　landslides　kept　stable　under　static　conditions　but　failed　when　the　SN　component　acceleration　reached　1.4　and　1.2　times　the　value　of　the　2014　Ludian　M-S　6.5　earthquake.　The　ground　motions　basically　correspond　to　the　earthquake　magnitudes　that　are　back-analyzed　by　their　volumes.　(5)　Both　the　penultimate　landslide　and　last　landslide　were　seismically　triggered　with　high　probability.　The　former　was　more　likely　due　to　the　seismic　activity　of　the　Zhaotong-Ludian　fault　than　the　Baogunao-Xiaohe　fault,　while　the　latter　might　be　induced　by　either　fault　which　was　active　since　the　Holocene.　Our　findings　present　new　insights　into　the　regional　seismological　history　and　considerations　on　the　risk　reduction　of　the　new　hydro-project　constructed　from　the　Hongshiyan　co-seismic　landslide　dam.