Abstract: Based on the definition of dollarcost averaging, the investment strategy was analysed quantitatively. The expression about the rate of stock return was achieved, and the main influence factors of stock yield were summarized through mathematical analysis. The investment strategy ensuring profit in the way of the dollarcost averaging was concluded: finding the company with well growth, choosing the security with lower costs according to the intrinsic value, and persevering in longterm investment by following the trends of the company growth. An empirical analysis has been conducted to verify the credibility of these principles. Generally, dollarcost averaging can not always assure the profit, but it provides the stock investor with an investment strategy to guarantee profit.

Key words: dollarcost averaging; company growth; intrinsic value; longterm investment