In this research,agriculture waste-rice straw was investigated as the sole carbon source as well as biofilm carrier to remove nitrate from wastewater in up-flow laboratory reactors. The experimental results indicated that the startup of the system was quick and a high nitrate removal efficiency was observed. The accumulation of nitrite was not observed in this process. Moreover, high nitrate concentration in the influent had a significant effect on nitrate removal efficiency. The reactor was able to accommodate a wide range of pH (6.5-8.5) and DO (1.0-3.5 mg/L). A time-dependent decrease in nitrate removal efficiency was observed after 84 days of operation. The results showed that rice straw could be used as an economical and effective carbon source for denitrification.