In spite of the wide use of plastics in engineering and everyday life,fundamental knowledge of the details in the glassy condensed state remain poorly understood1,2.Molecular dynamics simulations were used to investigate the conformational transition behavior in amorphous polyethylene with different chain lengths across the glass transition temperature(Tg).The motion heterogeneity of the systems were analyzed in detail and found the torsional transition rate distribution became gradually heterogeneous when the temperature went down to the glassy state.The molecular details of polymer glass transition were analyzed through the frozen torsions during our molecular dynamics simulations within different observation times.The glass transition temperature was found to coincide well with the temperature at which the frozen fractions were reduced to 1/e.The frozen chain segments grow as the temperature decreases in a similar way with that of linear polymerization,and the inverse number average frozen chain length leads to the formulation of configuration entropy during glass transition.The ideal glass transition temperature extrapolated to zero configuration entropy3 corresponds well with those reported in literature4,and the relation between the relaxation time and the configuration entropy shows perfect agreement with the Adam-Gibbs theory5 around the glass transition temperature.Volume spanning clusters are formed at the low temperature end,which might serve as a premature prototype for the formation of the ideal glassy state with limited accessible configurations.