Corn straw was used to improve the productivity of a red pigment during the biomembrane surface liquid cultivation of Penicillium novae-zelandiae. Both the dosage and particle size of corn straw powder had a significant effect on the fermentation period and pigment yield. After the optimization, the maximum yield of synthesised red pigment reached 0.43 g/L per day on day 9, which was 2.3 times higher than the initial productivity obtained by biomembrane surface cultivation without corn straw. An analysis on the mechanism suggested that corn straw shortened the fermentation period by providing the support for the growth of P. novae-zelandiae spores and biomembrane formation. Amino acids, including phenylalanine and tyrosine, released by corn straw, were the key reason for the improvement in the pigment yield. In addition, the increase of reducing sugars in the fermentation broth, due to the hydrolysis of cellulose and hemicellulose by the hydrolytic enzymes secreted by P. novae-zelandiae, provided a carbon source for fungal growth that might also be beneficial to pigment production.