Abstract: Two UASB reactors were used to evaluate separated-phase anaerobic treatment of a high strength wastewater. The granular sludge is well cultivated in both the methanogenic phase reactor and acidification reactor. In methenogenic phase,COD removal rate reaches 85%～90% when the organic load and HRT are at 88kg COD/m³bed . d and 3. 7h respectively. In the acid phase reactor,the VFA yield coefficient reaches 66% when organic load and HHT are at 240kg COD/m³bed . dand 1.6h respectively. COD removal rate reaches 4%～8%. Total COD removal rate reaches 92%,the organic load and HRT are at 60kgCOD/m³bed . d and 5. 3h. In this study,the maximum VFA yield coefficient reaches 70. l%,when organic load was 140kgCOD/m³bed . d,pH5. 3～5. 5,influent COD:TA 4. 4mg/mg. The characteristics of two-phase system were investigated in granular sludge formation and microbiological aspects.