Abstract: Abstract: Solid-phase denitrification (SPD) process is characterized by insoluble biodegradable polymers used as carbon sources. It is likely to avoid the risk of overdosing of liquid carbon sources in the conventional with the resultant deterioration of the effluent water quality. SPD process has been successfully applied on the treatment of groundwater and wastewater with a low ratio of carbon to nitrogen. This work was carried out in order to predict the nitrate concentration in the treated water and optimize the parameters using SPD process. A laboratory scale reactor was used, which was packed with the poly (3-Hydroxybutyrate-co-3-Hydroxyvalerate) (PHBV) granules as both carbon source and biofilm carrier for nitrate removal from the contaminated water. Based on Box-Behnken experimental design, the relationship among the effluent and influent nitrate-nitrogen concentrations, temperature and hydraulic retention time (HRT) was quantitatively investigated using response surface methodology. The calculated values of the equation were agreed well with the experimentally tested data, and their relative errors ranged from 1.5% to 19%. This equation can quantitatively describe the relationship among the effluent and influent nitrate-nitrogen concentrations, temperature and HRT. Influent nitrate-nitrogen concentration, HRT, temperature and their interaction had significant impacts on the response value by analysis of variance (P<0.05)．