The effect of microbial strains, spore suspension concentration and fermentation time on the isoflavone content of fermented soybean curd during the first fermentation period was investigated. The strains used were Actonomucor elegaus, Mucor wutungkiao and Rhizopusoligosporus saito. The results showed the isoflavone content differed dramatically depending on the strain used, and Rhizopusoligosporus saito could enhance the isoflavone content of the product by 133% and 90% compared to those with Actonomucor elegaus, and Mucor wutungkiao respectively.