Through data calculation, analyze the changes in the operating status of KFC, McDonald's and Burger King in recent years. Combining global dynamics in recent years, such as the Covid 19, to derive externally changing factors and explain how these external factors have affected operating conditions. Comparing the operating data of the three fast food chains, it is analyzed that the investment risk of Burger King is greater than that of the other two fast food restaurants, and due to Restaurant Brands International Inc. (the group to which Burger King belongs), Burger King is most affected by external factors. At the same time, because the localized menu adopted by Burger King lags behind that of KFC and McDonald's, and the 100% franchise model used has low-risk resistance capability, Burger King's global reputation and several stores are not as good as those of the other two. Therefore, in terms of business status and income, Burger King is not a better investment target.