Pipeline　leakage　can　lead　to　serious　environmental　damage　and　industrial　hazards.　A　spherical　detector　is　a　device　for　detecting　pipeline　leakage,　which　can　locate　the　leakage　position.　To　ensure　the　stable　operation　of　the　detector　in　a　variety　of　media　fluids,　this　paper　uses　the　numerical　simulation　method　to　study　the　motion　state　of　the　sphere　and　the　influence　of　different　density　fluids　on　its　motion.　It　is　found　that　the　resistance　and　lift　of　the　sphere　under　different　density　fluids　are　different,　which　will　affect　the　motion　trajectory　of　the　detector　and　the　speed　of　the　stable　stage.　Therefore,　the　working　environment　of　fluids　with　different　densities　needs　to　be　considered　when　designing　a　spherical　detector　to　ensure　its　stable　operation　in　various　fluid　media.　©　Published　under　licence　by　IOP　Publishing　Ltd.