The quality including in situ degradability in the rumen of Holstein of the black locust silage added with apple pomace was investigated in this study. The amount of apple pomace added in different treatments were 0, 20, 40 and 60% respectively. With higher amount of addition of apple pomace in black locust, crude protein content in the silage decreased. Crude protein contents in the apple pomace added silage were in the range between 11.7 and 13.7% and those were significantly lower than 16.3% of 100% black locust silage. The contents of ADF, NDF and crude ash were in the same trend as with crude protein, which were shown more clearly in the 40∼60% addition of apple pomace. Moisture content of 100% black locust silage was 56.7% however it significantly increased according to higher levels of addition of apple pomace(67.1∼73.8%). pH, lactic acid and total organic acid contents in 20∼60% addition of apple Pomace were 3.7∼4.3, 1.3∼2.2%, and 2.1∼6.0% respectively, however in 100% black locust silage those were significantly lower except pH as 5.4, 0.6% and 1.0% respectively. In situ disappearance rates of dry matter and NDF in the rumen were significantly higher at the stapes of incubation after 12h and 24h respectively in 20∼40% addition of apple pomace than in 100% black locust silage. No statistical differences were observed with quickly degradable fraction (a) in the disappearance rates of dry matter and NDF. In dry matter, however slowly degradable fractions (b) of 100% black locust and 60% addition of apple pomace were significantly higher as 99.7 and 99.8% respectively than 37.7∼50.5% of 20∼40% addition of apple pomace. On the contrary, fractional rate of disappearance (c) and effective degradability(ED) were significantly higher in 20∼40% addition of apple pomace as 0.0115∼0.0149 and 30.4∼31.9% respectively than the respective values of 0.0027 and 24.9% of 100% black locust. In NDF, b was significantly higher in apple pomace added silage(38.5∼99.8%) than in 100% black locust silage(14.9%). However, C was significantly lower in apple pomace added silage than in 100% black locust silage.