By means of the normal random walk (NRW) and self-avoiding walk (SAW) as the models of a polymer chain,the conformational properties of a polymer chain near an impenetrable plane were investigated,which gave the conformational entropy and chain size as functions of z0,the distance of one chain end to the plane．The computer simulation techniques used include the exact enumeration and Monte Carlo simulation．It was shown that the decrease in the conformational entropy of this confined polymer chain obeys a simple law．The reduction of achain in conformational entropy due to the confining effect of a surface increased with increasing the chain length and decreasing the distance z0．The mean square end-to-end distance (especially its z-component) of the confined polymer chain near an impenetrable plane was larger than the corresponding value of the free chain,as the end distance z0 was very small．When the end distance z0 increased the ratio of 〈R2〉 and〈R2z〉 decreased in the beginning,reached a minimum and then increased at last．As the end distance z0→∞,this ratio approached to alimit value equal to the corresponding value of a free chain．In other words,the size of the polymer chain wasexperienced a process of rapid contraction and then gradual extension．