The sample chains of polyethylene were set up by Monte Carlo simulation according to the real bond length and bond angle of PE and the conditional probabilities of a certain segment staying in one or another rotational isomeric state under θ conditions. The conformational number

the mean square end-to-end distance and its components of tail chains were calculated and compared with those from exact enumeration and theoretical deduction. The results indicated that:1) the method of Monte Carlo simulation is more accurate and converges much faster

2) the ratio of R2∥>/R2⊥>approaches 1/2 when the number of segments is large. It is in accordance with the theoretical deduction of half-space lattice model.The variation of conformational numbers and components of mean square end-to-end distance with number of chain segments and bond angle was also discussed. With the increase of bond angle

the number of conformation also increases

but the ratio of R2∥>/R2⊥> does not change much.