Adsorption kinetics of phenol on granular coconut shell activated carbon and granular coal based activated carbon was investigated by the model of homogeneous surface diffusion plus external film mass transfer with the stirred batch adsorber. The model was solved numerically by finite element and the parameter estimation was performed with the nonlinear least squares method. Through the confidence interval analysis and evaluation of the error sum of squares, higher precision of the parameter estimates can be obtained by combining more decay curves; the decay curves with the different initial solution concentrations and adsorbent dosages can be well represented with identical film mass transfer coefficient and surface diffusivity, and the effect of surface adsorption coverage on the surface diffusivity is negligible in the adsorption systems. The values of the film mass transfer coefficient and surface diffusivity are in the order of magnitude 10^(-5) and 10^(-12), respectively.