High　gain　DC/DC　converters　are　more　and　more　widely　used　in　new　energy　power　generation,　electric　vehicles,　uninterruptible　power　system,　smart　grid　and　other　new　applications.　And　the　development　trend　is　high　efficiency,　low　ripple,　low　stress　and　low　EMI.　A　high　step-up　Cuk　circuit　with　scalable　cell　was　proposed.　The　proposed　converter　not　only　inherits　the　traditional　Cuk＇s　advantages　that　the　continuous　input/output　current,　low　ripple　and　smaller　conducted　EMI,　but　also　achieves　high　voltage　gain　without　extreme　duty　cycle.　A　novel　high　step-up　Cuk　was　derived　by　combining　diode-capacitor　network　and　modified　step-up　Cuk.　Operating　principles　of　the　proposed　circuit　were　respectively　given.　Then　the　characteristics　of　the　proposed　circuit　were　analyzed　in　detail,　including　voltage　gain　characteristics,　main　parameters　and　the　voltage　or　current　stress　characteristics　of　semiconductor　devices.　On　the　base　of　these,　the　voltage　gain　of　the　converter　was　extended　further,　and　the　switching　voltage　stress　was　reduced　by　increasing　the　diode-capacitor　network.　Therefore,　a　main　power　switch　with　low　resistance　RDS　(ON)　can　be　used　to　reduce　the　conduction　losses　and　increase　the　efficiency　in　the　step-up　Cuk　with　scalable　cell.　Finally,　Computer　simulation　was　carried　out.　Four　100W　60V/400V　prototypes　were　designed　and　tested　with　other　typical　high　gain　converters　to　verify　the　validity　of　the　theoretical　analysis　of　the　proposed　circuit.　©　2019　Chin.　Soc.　for　Elec.　Eng.