Comparative religious studies is a new science that emerged in the second half of the 19th century through the efforts of Max Müller. Many years before this, Abu Rayhan Al-Biruni, an Iranian scientist of the 5th century AH (11th century CE), established a new approach in encountering other religions and explaining their beliefs and rituals. Al-Biruni's research method was based on four principles that Western scholars of religious studies later used to systematize their scientific method. These principles are: impartiality and lack of bias in research, empirical observation method, inter-religious comparison, and full attention to specific topics in religious studies. Al-Biruni, with an anthropological perspective, describes the beliefs of each group according to their condition and considering the mentioned principles, compares and explains these beliefs and ideologies. From the perspective of  Friedrich Max Müller, who is considered the founder of comparative religious studies, this branch of science has characteristics, including that it should be descriptive, objective, and free from bias and value judgment. In this article, we attempt to demonstrate that Al-Biruni's method of religious studies also possesses the elements and characteristics considered by Max Müller. Considering Al-Biruni's method and research, and his way of describing his observations, it is appropriate to consider him as one of the pioneers of this scientific field, even by the standards and criteria of great Western religious scholars like Max Müller.