Background and Objectives: Investigating performance of naturally operated treatment plants may be due to the fact that they cannot be operated as desired or should be modified to achieve good performance e,g for nutrients removal. The advantage of the kinetic coefficients determination is that the model can be adjusted to fit data and then used for analyzing alternatives to improve the process. This study investigates the efficiency of subsurface artificial wetland and determines its kinetic coefficients for nutrient removal. Methods: Present study investigated the kinetics of biological reactions occurred in subsurface wetland to remove wastewater nutrient. Samples were taken from 3 points of wetlands for 6 months. The nutrient content was determined through measuring TKN, ammonium, nitrate, and phosphate values. Results: Average levels for TKN, ammonium, nitrate, and phosphate in effluent of control wetland and wetland with reed were41.15, 23.59, 1.735 and 6.43 mg/l and 28.91, 19.99, 1.49 and 5.63 mg/l, respectively. First order, second order, and Stover-Keane Canon models were applied and statistical parameters obtained from the models (i.e. µmax،kB) were analyzed. Conclusions: The nutrients removal at Yazd wastewater treatment plant was remarkable and presence of reed beds has not a significant effect on system performance improvement. Other more efficient plants are suggested to be evaluated in the system. Stover-Keane Canon model provided predictions having the most significant relationship with actual data obtained from the field.