Abstract: The effects of substrate type and concentration on cultivation and stability of aerobic granular sludge are investigated.During start-up phase,sucrose is used as the sole substrate,compact aerobic granular sludge form in 10 days under influent COD concentration of 600-900 mg/L,the mean diameter of the granule is 1.15±0.14 mm,SVI is 90 mL/g.However,when the influent COD concentration is increased from 900 to 1 200 mg/L,outgrowth of filamentous bacteria in aerobic granular sludge occur,when SVI is increased to 175 mL/g and large amounts of aerobic granular sludge are washed out of the reactor.In order to control the filamentous growth in aerobic granular sludge,sucrose+peptone(1∶1) are used as the substrate under influent COD concentration of 600 mg/L,during 34 days,the filamentous bacteria gradually disappear,the filamentous growth aerobic granular sludge transits to stable smooth aerobic granular sludge again.When the influent COD concentration is increased from 600 mg/L to 1 200 mg/L,non-filamentous bacteria prevail and aerobic granular sludge are stable.This study shows that substrate diversity and increased substrate N/COD ratio leads to the control of filamentous growth in aerobic granular sludge.