We studied theoretically the translocation dynamics of polymer chain through a nanochannel, taking the position of its leading end in the channel as the reaction coordinate. The free energy profile of the translocation is found linear for homogeneous channels, and the driven force (the spatial derivative of free energy) is found insensitive to the chain length of the polymer, the length of the channel, whereas it decreases monotonically as the radius of the channel increases. Our Letter provides more direct understanding on recent experiments of polymer translocation. (C) 2013 Elsevier B. V. All rights reserved.