本文主要探討三種定期投資模式：定期定額、定期不定額和定期定值之投資績效表現，實際模擬回測2011至2020共計10年的投資狀況，並以元大台灣五十ETF(代碼：0050)為投資標的。主要比較內容為三種模式在2020年期末時的投資報酬率、投資期間報酬和現金流波動度、期末的資產狀態，並分析上述三種定期投資模式分別適合何種類型的投資人。
根據研究結果，定期定值擁有較高的報酬率，但也擁有最大的報酬率波動和現金流波動；定期不定額擁有次高的報酬率，其報酬率波動和現金流波動位居定期定值和定期定額之間；定期定額之報酬率為三者中最低，但其投資期間報酬波動和現金流波動度是三者中最低。考量風險後的報酬率，定期不定額之表現最佳，定期定額次之，定期定值則是最後。定期定額和定期不定額模式適合擁有穩定的現金流來源、不喜歡報酬波動太劇烈、追求長期投資和存股的投資人。定期定值模式較適合不想如定期定額和定期不定額般長期持有、對於現金流擁有較專業安排及調取能力，且願意承擔較大的風險換取較高額報酬率之投資人。
本文藉由研究三種定期式投資策略(定期定額、定期不定額、定期定值)實際模擬投資回測的績效以提供投資者參考及比較合種投資策略較適合自己的投資理念，並使對投資較無概念的投資人閱讀後具有一定的理解和方向。

The main purpose of this paper is to compare the result of backtesting Taiwan stock market by using three kinds of periodic investment strategy, which are Dollar-Cost Averaging, Transformed Dollar-Cost Averaging and Value averaging, and the investment target is Yuanta Taiwan 50 ETF (code: 0050). The comparisons include return on asset, return's volatility, cash flow's volatility and the asset status at the end of investing period. At the end of this paper will analyze which types of investors are suitable for the above three periodic investment models.
According to the empirical result, value averaging has the highest rate of return, but it also has the largest return's volatility and cash flow's volatility; Transformed dollar-cost averaging has the second highest rate of return, and its return's volatility and cash flow's volatility are among value averaging and dollar-cost averaging; Dollar-cost averaging has the lowest rate of return, and it has the lowest return's volatility and cash flow's volatility. As for risk-adjusted return, transformed dollar-cost averaging has the best performance, dollar-cost averaging is in 2nd place, value averaging has the lowest risk-adjusted return.
Dollar-cost averaging and transformed dollar-cost averaging are suitable for investors who have stable cash flow, don't like high volatility, and pursue long-term investing period. Value averaging is more suitable for investors who don't want to invest for a long time, and willing to take higher risk in exchange for higher rate of return.

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