©　The　Author(s)　2018.　The　vaned　diffuser　has　a　significant　impact　on　the　performance　and　operating　range　of　a　centrifugal　compressor　stage,　and　multi-row　vaned　diffusers　are　applied　to　improve　the　compressor　characteristics　in　this　article.　In　order　to　validate　the　effectiveness　of　the　present　calculation　method,　the　calculation　results　of　the　centrifugal　compressor　with　the　conventional　diffuser　have　been　verified　by　the　experimental　data.　The　simulation　results　reveal　that,　compared　with　the　original　model　at　design　point,　the　isentropic　efficiency　increases　by　2.8%　and　4.1%,　and　the　total　pressure　ratio　increases　by　1.9%　and　3.4%,　for　the　compressor　stage　with　the　two-row　vaned　diffuser　and　the　three-row　vaned　diffuser,　respectively.　The　models　with　multi-row　vaned　diffusers　also　give　higher　static　pressure　recovery　coefficient　and　lower　total　pressure　loss　coefficient.　A　pressure　gradient　formed　on　vane　suction　surface　near　vane　leading　edge　develops　the　flow　separation　in　the　conventional　diffuser.　The　pressure　gradient　thus　causes　the　secondary　flow　from　hub　to　shroud　on　vane　suction　surface,　aggravating　the　separation　in　the　rear　part　of　the　conventional　diffuser.　The　analysis　of　flow　characteristics　in　diffuser　passages　also　shows　that　using　multi-row　vaned　diffusers　can　alleviate　flow　separation　appearing　in　the　diffuser　passages.