＇three-year　mandatory　scrapping＇　policy　for　shared　bicycles　has　been　introduced　in　some　Chinese　cities　recent　years.　With　this　policy,　bicycle-sharing　operators　must　deal　with　the　contradiction　on　high　investment　and　long　payback　period.　From　the　perspective　of　bicycle-sharing　operators,　an　optimisation　model　is　first　proposed　to　determine　the　optimal　service　life　of　shared　bicycles　by　maximising　the　net　present　value　and　make　a　comparison　with　three-year　scrapping　period.　Second,　in　view　of　environmental　benefits　brought　by　bicycle-sharing,　the　service　life　to　offset　carbon　emissions　is　investigated　to　verify　the　policy＇s　reasonability.　Third,　Mobike,　OFO　and　Hellobike　are　taken　as　examples　to　discuss　what　parameters　affect　optimal　service　life　and　further　provide　some　management　insights　for　the　development　of　bicycle-sharing.　The　results　show:　when　the　diffusion　degree　of　quality　level　on　demand　is　low,　the　policy　is　unconducive　to　operators　with　high-quality　bicycles;　raising　rental　price　is　an　ineffective　way　to　increase　the　profit　of　operators;　the　service　life　to　offset　carbon　emissions　is　usually　within　three-year　scrapping　period,　but　it　depends　partly　on　the　replacement　ratio　for　different　transportations.　The　higher　the　replacement　ratio,　the　more　the　environmental　benefits　brought　by　bicycle-sharing.　(c)　2021　Institution　of　Chemical　Engineers.　Published　by　Elsevier　B.V.　All　rights　reserved.