Abstract: Broken coix seed, by-product of coix seed processing, was used as raw material of vinegar by liquid fermentation.The conditions of saccharification and acetic acid fermentation were optimized by single factor test and orthogonal test. The results showed that the optimal saccharification conditions were as follow: broken coix seed was crushed into 60 ⁸0 mesh further, the ratio of material to water was 1∶ 4 ( g/m L) and acid protease was added before saccharification.The optimal conditions for liquid acetic acid fermentation were static, temperature 32 ℃, inoculation amount 12% and loading volume 25%. Finally, total acid content of broken coix seed vinegar was 6.46 g/100 m L, typical-coix seed aroma, softer and clarification.