The purpose of the present studies was to determine the effect of the addition of Lactobacillus plantarum, rice bran and nitrogen source on the quality of silage. pH, organic acid and chemical composition of silage were measured during fermentation period from October, 1972 to March, 1973, and the results were as follows: 1. pH of silage was lowered to 4.2 by the maculation of Lactobacillus plantarum during the first week. 2. Lactic acid of silage was higher on the addition of Lactobacillus plantarum, rice bran end nitrogen source than control. Especially, multiplication effect was recognized from the simultaneous addition of Lactobacillus plantarum and rice bran. 3. Increasing ratio of acetic acid of silage was lower in the addition of Lactobacaius plantarum, rice bran and nitrogen source than control. 4. In the crude protein contents of silage, the effect of the addition of Lactobacillus plantarum and rice bran was significant, while that of the single inoculation of Lactcbacillus plantarum was insignificant. 5. During the period of fermentation, consumed quantity of N.F.E. was remarkable and the others showed low consumption of their quantity.