The emerging stock market in Viet Nam has been developed since 2006 and affected by the financial crisis 2007-2009. This study analyzes the impacts of tax policy on market risk for the listed firms in the electric power industry as it becomes necessary. rnFirst, by using quantitative and analytical methods to estimate asset and equity beta of total 20 listed companies in Viet Nam electric power industry with a proper traditional model, we found out that the beta values, in general, for many institutions are acceptable.rnSecond, under 3 different scenarios of changing tax rates (20%, 25% and 28%), we recognized that there is not large disperse in equity beta values, estimated at 0,486, 0,489 and 0,491.