Abstract: The diameter distribution of forest stands of broadleaved-Korean pine mixed forests on the Changbaishan Mountain was described by three distributions: exponential distribution, Weibull distribution and a finite mixture distribution,together with seven functions.Results showed that: 1) the diameter distribution was not the traditionally reversed J-shaped form but the rotated-sigmoid form;2) both the three negative exponential functions and a modified exponential function formed the reversed J-shaped curves and described the straight line in the form of the semilogarithmic plot;3) Weibull function built unimodal curve,but was not very effective;4) a finite mixture of two or three Weibull distributions was effective in modeling the diameter distribution of forest stands,but the finite mixture of three Weibull distributions was not notably better than that of the two Weibull distributions.