Bio-H 2 production from high-solid food waste using anaerobic mixed bacteria under thermophilic condition was operated at different total solids (TS) loading rates of 13.65, 27.3 and 40.95g/l/day. The system was configured to produce H 2 gas in conjugation with COD cr and nitrogen removal in a continuous stirred tank reactor (CSTR). The pH in H 2 reactor was maintained at a range of 5.0∼5.6 with circulation of supernatant from denitrification tank by circulation pump. The results obtained are as follows: Maximum H 2 production (4.01l-H 2/l/day) was achieved at the HRT 1.26d, which gave H 2 content of 55% and H 2 yield of 2.8 mol-H 2/mol-hexose. Continuous H 2 production was achieved for over 30 days at different TS loading rate. Only little amount of CH 4 at TS loading rate of 13.65g/l/day was observed. Total carbohydrate and TS removal efficiencies were 89 ∼ 98% and 60∼77% at each TS loading rate. Acetate and butyrate as major volatile fatty acid (VFA) were produced throughout experimental conditions and H 2 production increase with the increase of B/A ratio from 0.32 to 0.52 on a molar basis. This result suggests that stable H 2 production from high-solid food waste could be achieved at a range of pH 5.0∼5.6 by circulating supernatant from denitrification tank without adding chemical reagent.