Parameter estimation and statistical analysis of a new model for vanadyl etioporphyrin hydrodemetallization are performed using both the total sum of squares and the determinant criterion. Point parameter estimates are almost the same for the two objective functions, but the precision is increased when the determinant criterion is chosen. Subsequent statistical analysis shows the parameters are determined not badly, but slightly higher correlation between two parameters and nonrandom trends in residual plots are also detected. Failure in quantitative determination of the second intermediates and neglect of the tiny adsorption of the first intermediate on catalysts are ascribed to the deficiencies, respectively. As for the least-sum-of-squares estimator Monte Carlo studies suggest the bias due to the nonlinearity does not contribute much to the variances of the errors.