The numerical solution of a rate equation proposed by Sadler and Gilmer for the pinning of polymer crystallization has been examined to discuss the supercooling dependence of the kinetic barrier in comparison with that of surface nucleation postulated in the standard model. The entropy and free energy of the stems in the pinning region with the fluctuation of stem length have been evaluated from the stationary solution with the expression of conditional entropy of a finite Markov chain. The results have confirmed that the pinning stems form a local minimum in the free energy landscape and the rate-determining process is the detachment of the whole pinning region. The dependence on supercooling of the kinetic barrier is smaller than that of nucleation but not negligible for the parameters of polyethylene crystallization. (C) 2003 American Institute of Physics.