Probability has long been one of the subjects that attract me most. This researcher takes the moving molecular in the space as an example to transform it as a Random Walk, and study it through employing the concepts of the probability. This thesis manifests it can not prove its certain consequence following the theory of the first type of the reflex rate in the zero chapter of the Random Walk of the probability book by Karr, 1993 s. Hence this researcher adopts the methods of the convolution and Catalan number to substitute the previous method to identify the nature of the reflex rate, and it has got preliminary affirmative outcome.