The sand compaction pile method is the most frequently used methods as a countermeasure against liquefaction of sandy deposits. The design of the method, which is the determination of the replacement ratio with sand piles, is conducted by using the SPT N-value and fines content of a soil layer and the targeted N-value. This paper describes the relationship between the replacement ratios and the increments of N-values in between sand piles based on the field data obtained in ports and an airport in Japan. And the effectiveness of a conventional method for the determination of the replacement ratio is discussed with the field data. It is found that the N-value before compaction affects the increment of the N-value, and that the influence is not considered in the conventional method. A new method to predict the increment of N-values by compaction is proposed on the basis of the cyclic shearing mechanism of soil in between sand piles during compaction. The new method is validated with the field data.