Abstract: Ring-shaped polystyrene (RPS) was prepared through cyclization reaction of linear polystyrene with active end groups. Systematical characterization of RPS fractions was carried out by GPC-low angle laser light scattering spectroscopy and other methods. The mean value of the ratio g(=[η]_r/[η]₁) is 0.63 in θ solvent and ～0.65 in good solvents. The ratio of unperturbed mean square radius of gyration between ring and linear polystyrene (< R² >_oτ/< R² >_o1) is 0.55—0.59. They are both coincide with theoretical values for macro rings. It is found that RPS complys with universal calibration cuvve of GPC and has smaller hydrodynamic volume than linear polystyrene. Parameters of Mark-Houwink equations of RPS in cyclohexane 34.5℃,toluene 25℃ and tetrahydrofuran 30℃ have been obtained as K equals to 5.0, 0.683 and 1.2×10^-2;α equals to 0.5, 0.734 and 0.68 respectively.