Owing to an efficient quenching process that ensure r-poly(vinyl chloride) to be amorphous enough, crystallization of rPVC at lower temperatures has been found in samples with various processing histories. Through a modified Avrami analysis, kinetics of the isothermal crystallization at these low temperatures was studied, proving that the crystal growth in the studied temperature range was controlled by segment mobility, which should follow a WLF-type relationship. Such a mechanism is unusual compared to ordinary growth controlled by chain reptation. Also discussed were implications of the results to further crystallization study of PVC and to that of polymers in general. The treatment distinguished itself in that it can give out both spacial growth exponent and dependency of the dimension on time.