This experiment was conducted to find out the change of composition and yield of whole crop rye plant by the maturity stage such as boot, heading, milky, dough and yellow ripe. The results of this experiment were as follows: The yield of whole plant was significantly (P<0.01) higher in the dough stage than in the other stages, and stalk yield of whole plant was significantly (P<0.01) higher in the dough stage than in the other stages, and stalk yield of whole plant was the highest in the part of whole plant, ear yield in the yellow ripe stage. Leaf and stalk yield in the ratio of part yield to whole plant yield remarkably decreased according to the passage from boot to yellow ripe stage, but ear yield increased. Dry matter yield increased with advancing maturity stage, and was the highest in the yellow ripe stage (P<0.01). Crude protein contents of whole plant and each parts gradually decreased, and crude fiber content increased with advancing maturity stage.