This study was aimed to determine the effects of different levels of fresh whey and Lactobacillus buchneri inoculation on the nutrient properties and aerobic stability of alfalfa silage. Experiment was conducted with 8 treatments and 3 replicates for 90 days. Treatments included wilted alfalfa (control), wilted alfalfa + bacterial inoculant (AB), wilted alfalfa +30 g whey/kg (AW1), wilted alfalfa + 30 g whey + bacterial inoculant (AW1B), wilted alfalfa + 60 g whey per kg (AW2), wilted alfalfa + 60 g whey per kg + bacterial inoculant (AW2B), wilted alfalfa + 90 g whey per kg (AW3) and wilted alfalfa + 90 g whey + bacterial inoculant (AW3B). Results showed that, the pH values of treatments were found less than 4.86 but the control pH was higher in comparison with other treatments (P<0.05). The addition of fresh whey and complementary bacterial supplement to alfalfa caused a significant increase in total fatty acids. There was no significant difference between neutral detergent fiber (NDF) and acid detergent fiber (ADF) in all treatments compared to control group. The least resistance to erosion was related to wilted alfalfa + bacterial additive (AB), and the highest amount was related to wilted alfalfa + 60 g whey (AW2: P<0.05). The results showed that fresh whey and bacterial inoculation with the fermentable carbohydrates leads to rapid reduction of pH, limiting the proliferation of yeasts, increased aerobic stability and improved silage quality.