Abstract: A method for forecasting a WIP (work in process) output schedule and a computer program product thereof are provided. A plurality of sets of historical WIP data regarding a product generated in respective historical periods are first collected, in which the product has a maximum historical production cycle. Thereafter, a predetermined time is used to divide the maximum historical production cycle into intervals. Then, the quantities of historical WIPs appearing in the respective intervals are computed in accordance with output times of the historical WIPs recorded in each of the sets of historical WIP data, thereby obtaining output probability density data series. If the number of the historical periods is greater than or equal to a minimum model-building number, a predicted output probability density data series of a next period following the historical periods is conjectured by using the output probability density data series in accordance with a prediction algorithm.