Abstract: Using the statistic of living binary copolymer to treat the product of first method, we get the distribution of MW and degree of branching with different MW of Prepolymer.In the system of living polystyrene, p-DVB and benzene, we synthesize star polymer under high vacuum.In definite range of temperature, concentration of active species, experience data reveals: coefficient of polydispersity concids with theoretical result, furthermore no matter how wide MWD of prepolymer we have, the MWD of product still remains relative narrow. The degree of branching depends on initial material ratio (A=M₀/I₀) and the conversion of DVB's second double bonds for branching f_x. The relatinship is expressed by Eq. (10). As initial A increase, MWD is Broaden and deviation from Eq. (10) appears. The reason is there are some crosslinking took place between star polymers. Finally, gel point is reached. The critical ratio is 9 for low MW of living polymer, for high MW prepolymer, critical ratio shall be increased.In short, the model of living binary copolymer is good for treating star polymer in low initial ratio, it needs some correction for high ratio.