The present study deals with the performance evaluation of the UASB reactor under varied organic loadingrate(OLR) for the treatment of paper mill wastewater. The sludge granulation process started after 120 days from thed) the VSS concentration was 12.86 gVSS/L, which got increased to 38.05 gVSS/L at the end of an OLR 2.1process. Many times the pH observed was between 6.5 and 7.8, which is more favorable for any anaerobicprocess. It is also found that pH within the reactor increases along with the height of reactor. The total maximumremoval at this stage was observed to be 90%.