The outline of this paper is: 1st. To make a study of the routes followed by Huien Tsang and Sudhadana in India. 2nd. To study the geography, geology, climate and connections of those routes in order to assess their importance and contribution to the early Indian history. 3rd. To compare the time of compilation of the Hwa-ying sutra with the time when Huien Tsang visited India. Next, we will try to determine the influence and contributions of them. In my conclusion, I have pointed out the major points of this article related to the following four aspects. i) Study of the two visitors' routes in India; ii) Determination of their importance to the early history of India; iii) Evaluation of the influence exerted by the two visitors; iv) Examination of the main contributions of them.