Conformation statistical theory of polymeric chains is essential to the understanding of the concept of Gaussian chain. It is the base of the statistical theory in polymer science. Kuhn’s method is the mostly described one in textbooks of polymer physics. But the mathematical steps are complex

which is hard to be comprehended by the students. Meanwhile

some flaws exist in it which hinders the understanding of the concept of Gaussian chain and has a negative impact on the study of statistical theory of polymer dilute solution and rubber elasticity. The Kuhn’s method is modified based on central limit theorem. Two methods for calculating the mean square end-to-end distance are introduced. These methods are concise and explicit

which are easy to understand and be beneficial for the students to catch on the concept of Gaussian chain.