The objective of this study was to evaluate the effects of replacing corn silage with barley silage according to undigested neutral detergent fiber on lactation performance, nutrient intake and digestibility, feeding behavior and income over feed cost of Holstein dairy cow in early lactation. In this experiment, 8 Holstein lactating cow (parity two or higher), 81.8 ± 10.1 days in milk; milk production = 58.5 ± 4.55 kg; body weight = 639.6 kg and body condition score =3.3 ± 0.49 (mean ± standard deviation) were assigned to a replicated 4 × 4 Latin square design. Experimental treatments were: 1) control diet containing 100% corn silage 2) Replacing 33% of corn silage with barley silage; (3) replacing 67% corn silage with barley silage; and (4) replacing 100% corn silage with barley silage. The diets were balanced according to energy, protein and undigested neutral detergent fiber for 30 hours incubation. Replacing of corn silage with barley silage resulted in a linear increase (P 0.01) of residual particles size of the total mixed ration on a 19 mm sieve and a linear decrease (P 0.01) of residual particles size on a 8 mm sieve, but no differences observed i the residual particles of 1.18 mm sieve. Physical Effective NDF larger than 8 and 1.18 mm also tended to increase linearly (P= 0.07). Replacement of corn silage with barley silage did not affect on ruminating time and resting behavior, but eating time and total time chewing was decreased quadratically. milk production, 3.5% fat corrected milk and milk composition were not affected by treatments. undigested neutral detergent fiber 288 hour intake as a percentage of dry matter increased linearly with increasing levels of barley silage in the diet (P 0.01), but there was no difference in the consumption of potentially digestible neutral detergent fiber (pdNDF) among treatments. Replacing corn silage with barley silage did not have any effect on dry matter and organic matter intake, and resulted in the same nutritional efficiency,but decreased ether extract intake (P 0.01) and increased linearly NDF intake (P 0.01). Apparent total tract digestibility of dry matter and organic matter decreased linearly with increasing barley silage in the diet (P 0.01), but no difference was observed in the digestibility of NDF and crude protein. Rumen and feces pH was not affected by experimental treatments, but ruminal ammonia nitrogen increased linearly with increasing barley silage levels in the diet (P 0.01). Plasma Beta hydroxy butyrate concentration decreased linearly with increasing dietary barley silage (P= 0.02), but there was no difference in Blood urea nitrogen and glucose concentrations. Replacing corn silage with barley silage reduced the price per kilogram of ration dry matter and income over feed cost tended to increase linearly. Overally, The results of this experiment showed that replacing corn silage with different level of barley silage according to undigested neutral detergent fiber in the Holstein dairy cows dietary did not affect their performance and barley silage can be a good alternative to corn silage, especially in conditions of water shortage. Keywords corn silage, barley silage, uNDF, dairy cow performance