First-principles calculations based on density-functional theory and the generalized gradient approximations have been carried out to investigate interface properties of β-Si3N4/Si(111) systemically. An interface structure without dangling bonds at the interface was proposed, and this interface structure was found energetically more favorable than the existing model. Perfect bonding structure and strong Si–N bonds at the interface due to the charge transfer from Si atoms to N atoms result in this stable interface structure. The calculated band offsets of this interface structure are in agreement with previous theoretical estimations and experimental results. Besides, we also studied the effects of dangling bonds at the interface on electronic properties of β-Si3N4/Si(111). Dangling bonds would slightly decrease the valence band offset and generate gap states at the interface. The hydrogen saturated interface shows better electronic properties but the low dissociation energy of Si–H bonds would be a problem in applications.