The　water-meter　shell　has　a　complex-structured　thin-walled　cavity,　and　it　can　cause　casting　defects　such　as　shrinkage　and　misrun.　On　the　basis　of　structural　analysis　of　a　water-meter　shell,　a　three-dimensional　model　and　a　finite　element　model　of　the　water-meter　shell　were　constructed　using　the　SOLIDWORKS　and　ProCAST　software　as　a　modeling　tool　and　a　casting　numerical　simulation　tool,　respectively.　Three　processes　associated　with　the　bottom　gating　system　without　a　riser,　a　step　gating　system　with　a　preliminary　riser,　and　a　step　gating　system　with　an　optimum　riser　were　successively　numerically　simulated.　The　mold-filling　sequence,　temperature　distribution,　liquid-phase　distribution　during　solidification,　and　shrinkage　distribution　of　these　three　processes　are　discussed　here.　The　numerical　simulation　results　indicated　that　optimization　of　the　casting　process　and　the　rational　assembling　of　the　riser　led　to　the　shrinkage　volumes　at　the　inlet　position,　regulating　sleeve,　and　sealing　ring　of　the　water-meter　shell　decreasing　from　0.68　to　0　cm(3),　1.39　to　0.22　cm(3),　and　1.32　to　0.23　cm(3),　respectively.　A　comparison　between　model　predictions　and　experimental　measurements　indicated　that　the　castings　produced　by　the　optimized　process　had　good　surface　quality　and　beautiful　appearance,　without　casting　defects,　demonstrating　that　numerical　simulation　can　be　used　as　an　effective　tool　for　improving　casting　quality.