Abstract:The project was carried out to find out the impact of stock split on the stock market. In our project, we used event study methodology to evaluate the accuracy of stock price reaction of 39 Indian companies listed on the National Stock Exchange (BSE) in 2006 and onwards. The results of abnormal returns (actual returns-returns from the regression line) were taken for 20 days before and after the announcement date to check whether the result is significant or not (significance level = 5%). The project shows that there is no significant difference in the price level before the announcement date while after the announcement date there was a significant difference in the price level for some days (significance level is 5%). The project supports the hypothesis that India's stock market is semi-efficient. Stock market efficiency: Market efficiency means how “quickly and accurately” relevant information has its effect on asset prices. Depending on the degree of efficiency of a market or its sector, the return obtained by an investor will vary compared to the normal return. The efficient market hypothesis states that it is not possible to consistently outperform the market using any information already provided by the market. he knows, if not by luck. Information or news in the EMH refers to anything that can influence prices, which is unknowable in the present and therefore appears randomly in the future. Introduction: An event study uses transaction data from financial markets to predict financial gains and losses associated with newly released information. For example, the announcement of a merger between two companies can be analyzed to make predictions about potential merger-related changes in the supply and price of the merging products. Event studies seek to analyze the impact of a specific class of events on security prices. The most popular use of the event study is in testing the efficient market hypothesis (EMH). Efficiency is demonstrated by showing that the market response to an event occurs before the event or shortly after the event: information is anticipated or assimilated very quickly. Pioneering work on the study of events was done by Ball and Brown (1968) and Fama, Fisher, Jensen, and Roll (1969) (henceforth referred to as FFJR). The methodologies used in these studies have become a standard technique for testing EMH. Over the past two decades a series of events such as stock split announcements, earnings announcements, mergers and acquisitions have been studied by researchers to examine market efficiency.