Abstract: Based on the experimental data of number-average and weight-averge molecular weights,a general technique is developed in this work for simulating viscosity-average molecular weights.In the cases of polymer composition respresented by either Weibull distribution or logarithmic normal distribution,the equations are first set up for simulating viscosity-average molecular weights.Further more,this study indicates that the simulation results with respect to these two distributions become identical as a approaches unit in good solvents in which the large winded polymer molecules spread to form a variety of random coils in configuration.The experimental data substantiates the above conclusion.Finally it suggests in this study that because of the simplicity of logarithmic normal distribution in form,it is fairly wie ldy in simulating viscosity-average molecular weights for the case of the polymers with narrow andmiddle-broad distribution,and broad distribution in good solvents.