A method for loading fuel pellets for manufacturing a nuclear fuel rod is provided. The method includes arranging fuel pellets in a row on a tray, aligning the fuel pellets in the row on the tray such that the fuel pellets are closely in contact with one another, obtaining a total length of the pellets in the row by measuring the fuel pellets in the row on the tray, and comparing the total length with a predetermined length. When the total length is smaller than the predetermined length by a difference greater than an average unit length of the pellet, one or more fuel pellets are added in the row until to increase the total length until the difference becomes smaller than the average unit length of the fuel pellet.