A method for prediction in image encoding and an image encoding apparatus applying the same are disclosed. The method includes steps of receiving a plurality of candidates with respect to a current prediction target of an image; calculating a distortion-based cost of a first candidate in the plurality of candidates; and for each of the other candidates, computing a data access availability and a data access requirement for calculating a distortion-based cost of a current candidate in the other candidates of the plurality of candidates; and if the data access requirement does not exceed the data access availability, calculating the distortion-based cost of the current candidate; otherwise, selecting the candidate with the minimum calculated distortion-based cost as a matched candidate for the current prediction target. Therefore, coding performance setback due to external memory data access is improved.