Polyurethane Foam (PUF) was used as inert supports in solid state fermentation (SSF) for cellulase production. The effects of PUF size and PUF weight percentage to solid substrates were investigated. When compared with the control without PUF, the maximal enzyme yields in batch fermentation were improved by 70.6% and 60.4% for Filter Paper Activity (FPA) and CMCase, respectively. With PUF, higher FPA and CMCase could be obtained even when the depth of the substrate was 1.5 times than that of the control which is conducted under optimal substrate depth without PUF. Moreover, a promising method for semi-continuous SSF was also tried to be developed by using adsorbed cells in PUF for several cycles.