A general logarithmic normal distribution is developed for simulating the molecular weight distribution of non-degradation polymers. Based on gel permeation chromatography data of number-average and weight-average molecular weights, a set of equations is derived to evaluate all averages of and all moments of polymer molecular weights. Results obtained from theoretical considerations demonstrate that the general logarithmic normal distribution is essentially independent of the distribution exponent, and as a consequence, Wesslau’s and Koningsveld’s distributions are identical in nature. Simulation experiments substantiate the above conclusion.