In an air jet loom, compressed air is used for the insertion of the weft yarn . To make compressed air, much electric power is necessary ; the power is two or three times higher than that used in other waving mechanical motions. From energy reduction point of view, a new apparatus which reduces the energy for the insertion has been developed. In this work, the ability of a new apparatus which assists mechanically the weft yarn insertion is assessed. From the assessment, it is found that the apparatus is markedly efficient for the insertion of the weft yarn. That is, the energy consumption of the compressed air is found to be reduced from 10 to 30 % by using the supplementary apparatus.