This paper presents isolated high boost dc-dc flyback converter with high voltage gain suitable for renewable energy source. The circuit consists of active clamp circuit and boost converter with isolated transformer. The circuit employs capacitors are charged in parallel and discharged in series by isolated transformer inductors. The active clamp circuit is used during the turn off-period to reduce the voltage spike on power switch. To achieve high output voltage gain the flyback converter output terminal and boost converter output terminal are connected in serially with the isolated inductors with less voltage stress on controlled power switch and power diodes. PSIM software has been used for simulation. Hardware model implemented and tested in the laboratory. © 2013 Praise Worthy Prize S.r.l. - All rights reserved.