An electrochemical N2 reduction reaction (NRR), as an environmentally benign method to produce NH3, is a suitable alternative to substitute the energy-intensive Haber-Bosch technology. Unfortunately, to date, it is obstructed by the lack of efficient electrocatalysts. Here, a CoS2/MoS2 nanocomposite with CoS2 nanoparticles decorated on MoS2 nanosheets is fabricated and adapted as a catalyst for the NRR. As unveiled by experimental and theoretical results, the strong interaction between CoS2 and MoS2 modulates interfacial charge distribution with electrons transferring from CoS2 to MoS2. Consequently, a local electrophilic region is formed near the CoS2 side, which enables effective N2 absorption. On the other hand, the nucleophilic area formed near the MoS2 side is in favor of breaking stable N≡N, the potential-determining step (*N2 → *N2H) which brings about a much decreased energy barrier than that on pure MoS2. As a result, this catalyst exhibits an excellent NRR performance, NH3 yield and Faradaic efficiency of 54.7 μg·h-1·mg-1 and 20.8%, respectively, far better than most MoS2-based catalysts.