We studied the Internal Circulation (IC) anaerobic reactor start-up progress in treating juice wastewater. The results shown that IC reactor has certain acidoresistant, the pH of inflow water can drop to 6.0, the IC reactor under the circumstance of increasing COD concentration gradually to enhance the volume load, sludge bed zone of the reactor IC was filled fully by granular sludge with good settling property little by little as reactor run .In the bottom of the reactor, granular sludge particle size in 2-3mm were more. And particle size of all the granular sludge under the sludge bed zone was bigger than that the upper. When the COD concentration was about 7000mg/L, HRT remained unchanged for 12 hours. Under the Circumstance of the volume load in 14.15kgCOD/m3.d,COD removal rate kept above 90%. Effluent volatile fatty acids (VFA )stabled at less than 400mg/L.