The field of methodology has been an active area of philosophy of science-epistemology- over the past few decades. Methods, models, and paradigms have multiplied and transformed themselves with dizzying speed, fostering a burst of interest in a heretofore-moribund topic. Methodology defines the most important cleavages within the educational sciences today. According to Wright Mill: "Methodologist gets to work!" However, the question naturally arises, how is one to go to work? In addition, what is one to work on? Hargreaves emphasized that there is a considerable amount of second rate educational researches which: (1) dose not makes a serious contribution to fundamental theory or knowledge. (2) Is irrelevant to practice (3) is uncoordinated with any proceeding or follow-up research (4) clutters up academic journal that virtually nobody read. Therefore, it is appropriate to revisit its roots and to examine how it is possible to inquire educational activities and environments. This paper will reference to some common fallacies in educational research that are related to relationship between theory and practice. I believe that: The performance is a realist, although, in a transcendental sense. Purpose of this article is expressing some function methodology and explaining them based on the methodological theory. At this time, there are two perspectives (methodological theory) that all of the research methods have derived from them: 1- Empiricism, include positivism and critical rationalism 2- interpretative approach. However, this paper is articulating some function methodology that is derived from positivism and critical rationalism. In other words, studying relation between methodology and research method, based on two methodological approaches as mentioned above, is the main purpose of the paper. Therefore, the area of this methodology and research method firstly will be expressed; then some implications of the methodological theory to educational research, as a practice will be explained. These help to indicate there are some binary oppositional ideas on the methodological theories. In this paper, comparing two methodological theories, positivism and post- positivism, will be done in terms of the major themes. The fundamental terms are nomothetic versus idiographic, subjectivity versus objectivity, certainty versus relativity, deductive thinking versus inductive thinking, neutral versus theory-laden methodology, incommensurability versus commensurability questional versus problematic characteristic of scientific method, hypothesis versus proposition and top-down versus bottom-up approach to educational research . Some preliminary results can be identified as follow: Where the positivist believes that the goal of science is to uncover the truth, the post-positivist critical realist believes that the goal of science is to hold steadfastly to the goal of getting it right about reality, even though we can never achieve that goal, because all measurement is fallible. While Positivists believes that objectivity is a characteristic that resided in the individual scientist and scientists are responsible for putting aside their biases and beliefs and seeing the world as it 'really' is, post-positivists reject the idea that any individual can see the world perfectly as it really is and then they emphasizes the importance of triangulation (multiple measures and observations). Post- positivists consider deductive method in experimental research and so suggest the scientist should be investigated by top-down approach. On the other side, positivists strongly emphasize inductive method and so recommend bottom-up approach to scientific research.