Abstarct: The purpose of this study is studying the impact of speculation on price volatility, baxsed on two theories of rational speculation and inventory at the level of companies listed on the Tehran Stock Exchange. The statistical sample of this research includes 98 selected companies during the years 1392 to 1397. Excel and EViews software have been used to classify, process and analyze the data. The variables of this research include stock price fluctuations, daily trading percentage and margin trading percentage and control variables. The size of the company is the change of legal ownership, the change of real ownership and the final price. In order to test the research hypothesis, logistic regression and multiple regression tests have been used. The results obtained baxsed on two methods show that in all tests, the two variables of rational speculation and retention have a positive effect on stock price fluctuations, although the effect of rational speculation is greater than retention speculation. The results also showed that speculation increases the likelihood of increased stock price fluctuations. Control variables also have different effects on stock price fluctuations. So that the variable of company size and change of real ownership in the logistic regression test has a negative effect on fluctuations, but in the regression, test has a positive effect. The final price variable also has a positive effect on logistic regression test but has a negative effect on stock price fluctuations in multiple regression.