A high kojic acid producing mutant UV3x3 was screened out from an Aspergillus flavus strain A-5 using UV mutation technique. The strain produced 6. 84g/100mlkojic acid in 6 days under an optimal shaking flask cultivation condition:temperature, 33 ℃;corn starch, 14%; yeast extract, 0. 5%; H3PO4, 0.07%; MgSO4· 7H2O, 0. 05%; FeSO4.7H2O, 0. 002 %; K2CO3, 0. 03 %. The overall productivity was 11. 4g/ (1. d ) and 15. 4g/ (1. d )was reached in the later period, with conversion yield of 55% on the reducing sugar co...