Although typhoon forecasting has been improved notably over the years, it remains a difficult challenge to make timely and accurate rainfall forecasts, which is crucial to saving lives and reducing damage. Under the assumption that a proportional relationship exists between the accumulated rainfall of a typhoon hitting Taiwan and climatological accumulated rainfall, the Rainfall Potential Analog Forecasting (RaPAF) technique is proposed for predicting the accumulated rainfall distribution when a typhoon makes landfall in Taiwan by an analog forecasting technique. The RaPAF is a combined method involving an operational SSM/I rainfall retrieval algorithm, the tropical rainfall potential technique, and an empirical relationship of precipitation associated with typhoon. In addition, The RaPAF needs information on forecast of typhoon track as an input. In the case study of Typhoon Morakot (2009), it is proven that the method not only provided a more accurate accumulated rainfall distribution prediction and that the probable mapping of the maximum precipitation areas was also close to the actual observations. The calculations involved were easy and quick to implement, enabling it to serve as a viable tool for producing accumulated rainfall forecasts and potential damage assessments during different stages after typhoon genesis. The RaPAF technique may be useful for accumulated rainfall prediction of typhoon.