Many　cities　around　the　world　face　the　challenge　of　an　aging　population.　A　full　understanding　of　the　mobility　behavior　characteristics　of　the　elderly　is　one　necessary　and　urgent　consideration　as　regards　the　current　aging　trend　if　sustainable　urban　development　is　to　be　fully　realized.　This　paper　presents　a　systematic　approach　to　analyzing　the　dynamic　mobility　characteristics　of　the　elderly　who　travel　by　bus　using　smart　card　big　data.　The　characteristics　include　temporal　distribution,　travel　distance,　travel　duration,　travel　frequency,　and　also　the　spatial　distribution　of　such　travelers.　The　findings　of　these　mobility　characteristics　can　directly　contribute　to　both　public　transport　policy　making,　service,　and　management.　In　this　study,　the　analytics　of　the　elderly　are　also　compared　with　that　of　the　average　adult　group　so　as　to　identify　both　the　similarities　and　differences　between　the　two　groups.　Beijing,　a　megacity,　with　a　very　high　life　expectancy　and　in　which　the　bus　is　the　dominant　mode　of　public　transport　for　the　elderly,　was　used　as　the　study　area.　The　significance　of　this　research　concerns　a　newly　developed　systematic　approach　that　is　able　to　analyze　the　dynamic　mobility　characteristics　of　the　elderly　using　smart　card　data.