Abstract: Polydimcnsional Poisson's distribution function, which can characterize both molecular weight and arbitrary length segment distributions of the binary living copolymers, has been first derived by the method of combining probability with kinetics. It can be transformed into poly-dimensional Gaussian distribution for simplifying calculation. Aformula for calculating the theoretical GPCchromatogram of the product in the living binary copolymerization has also been obtained by using this distribution function and the additivity of hydrodynamic volumes