The　Cu/SAPO-18　samples　with　different　Cu/Al　mass　ratios　were　prepared,　their　catalytic　activities　for　the　NH3-SCR　of　NO　in　simulated　diesel　exhaust　were　evaluated,　and　effects　of　Cu/Al　mass　ratio　and　hydrothermal　aging　temperature　on　catalytic　performance　of　Cu/SAPO-18　was　examined.　Physicochemical　properties　of　the　samples　were　characterized　by　means　of　various　techniques.　It　is　found　that　the　activity　of　the　sample　changed　with　a　rise　in　Cu/Al　mass　ratio,　with　the　highest　overall　activity　being　achieved　over　the　sample　with　a　Cu/Al　mass　ratio　of　0.045.　The　H-2-TPR　results　indicate　that　the　Cu/Al　mass　ratio　could　affect　the　distribution　of　Cu　species,　and　the　Cu/SAPO-18-0.045　sample　possessed　the　highest　amount　of　the　isolated　Cu2+　species.　BET　and　XRD　results　reveal　that　the　Cu/Al　mass　ratio　exerted　little　effect　on　the　structure　of　the　sample.　Low-temperature　hydrothermal　treatment　had　the　least　influence　on　the　sample,　and　the　effect　of　high-temperature　hydrothermal　treatment　on　the　sample　became　increasingly　obvious　with　a　rise　in　hydrothermal　treatment　temperature.　It　is　concluded　that　the　hydrothermal　aging　treatment　mainly　affected　the　sample　by　destroying　the　structure,　blocking　the　pores,　migration　and　transformation　of　the　Cu　species,　and　changing　the　acidic　sites　of　the　sample.