The old problem of glass transition is regarded as the most important behavior of polymer science, while the fundamental microscopic picture of the polymeric glass-formers is scarcely seen. By way of atomistic molecular dynamics simulations the microscopic local dynamics were analyzed through the conformational transition behavior across a wide range of temperatures. Such local dynamics were found becoming gradually heterogeneous when the temperature went down close to the glassy state. The frozen torsions were determined through a time dependent fashion, and the statistics related to the frozen fraction and frozen chain length showed that the local dynamics of conformational transition corresponded well with the classical thermodynamic or kinetic theories. The frozen chain segments grew as the temperature decreased in a similar way with that of linear condensation polymerization, and the number average frozen chain length were related to the configuration entropy deduced from network polymers during chemical vitrification. The relation between the torsional relaxation time and the configuration entropy showed perfect agreement with the Adam-Gibbs theory around the glass transition temperature. The frozen torsions expanded with further decrease of temperature until the formation of a volume spanning cluster, which might serve as a premature prototype for the formation of the ‘ideal glassy state’ with limited accessible configurations.