In this work,Monte Carlo simulations are used to study the critical adsorption behaviors of flexible polymer chains under the action of an external driving force F parallel to an attractive flat surface.The critical adsorption temperature Tc decreases linearly with increasing F,indicating that the driving force suppresses the adsorption of polymer.The conformation of polymer is also affected by the driving force.However,the effect of F is dependent on the competition between the driving force and temperature.Under strong force or at low temperature,the polymer is stretched along the direction of the force,while under weak force or at high temperature,the polymer is not stretched.When the force is comparable to the temperature,the polymer may be stretched perpendicular to the driving force,and below Tc,we observe conformational transitions from parallel to perpendicular and again to parallel by decreasing the temperature.We found that the perpendicular stretched conformation leads the polymer chain to synchronously move along the direction of the driving force.Moreover,the conformational transitions are attributed to the competition and cooperation between the driving force and the temperature.