IntroductionThe efficiency of financial markets is one of the major research and testing topics in the financial field. Many economists have done a lot of research on this important area and intend to find the best way to illustrate the results of financial market definition. In recent years, research and testing have become the basis for investors to consider investment stages. This movement is important since the market can change at any time. The concept of efficient market hypothesis is defined as there are many potential investors in the market who try to compete with each other by predicting the future of the company's stock or any other investor. other financial securities, the company's information about which was available to all investors and the price of securities and shares is reflected in the information that the company properly discloses. (Eugene. F, 1965) The market efficiency hypothesis can be divided into three different stages: weak efficiency form, semi-strong efficiency form and strong efficiency form. By reviewing research and testing, this essay aims to compare three different forms of efficiency market hypotheses and the empirical studies that have been conducted to assess the validity of each form. In this essay, it will contain three main parts to illustrate the research and compare between the three forms of efficiency included the random walk theory. First, we will look at the random walk theory and see how it will affect stock prices under the weak form of the efficient markets hypothesis. Then follow the evaluation of empirical studies on the weak form of effectiveness. Second, explain and compare the semi-strong form of the efficient market hypothesis which differs from the weak form...... middle of article...... However, insider trading is illegal these recent years, which is limited by law because it is not fair to other small investors. (Seyhun, 1986) Conclusion Efficient market hypothesis is an important step in predicting the future price of stocks or securities in the short term. By applying the new information to respond to the company, it can help identify the direction of the stock price and achieve returns. Although the result may fail for the long-term investor, it is still useful for investors who intend to invest in the short term. Reacting to favorable or unfavorable information for the company can help adjust overvalued or undervalued stocks to maintain market balance. Since EMH can still be the basis of stock price prediction, EMH is still viable for investors to study and review before investment..