Uniform and dense zeolitic imidazole framework-8 (ZIF-8) sub-layer was fabricated on the surface of polyvinylidene fluoride (PVDF) membrane via an in-situ contra-diffusion method, and the interfacial polymerization (IP) procedure was further used to prepare polyamide/ZIF-8/PVDF composite nanofiltration (NF) membranes with polyamide (PA) top thin layers and ZIF-8 sub-layers. SEM, XRD, FTIR, AFM, XPS, contact angle analyzer and zeta potential analyzer were utilized to measure the chemical compositions, structures and morphologies of the prepared ZIF-8/PVDF composite membranes and the PA/ZIF-8/PVDF composite NF membranes. The effect of ZIF-8 sub-layer on the structure and performance of these composite NF membranes were investigated systematically. Results indicated that the existence of ZIF-8 sub-layer increased the crosslinking degree of the polyamide and improved the compatibility of polyamide layer and PVDF support membrane. Under the pressure of 0.6 MPa, the composite NF membrane exhibited high flux of 24.05 L/m2?h and good anti-fouling property. Furthermore, the composite NF membranes showed excellent desalination performance, with the rejection ratio of 97.34%, 93.57%, 89.31% and 85.16% for MgSO4, Na2SO4, NaCl and MgCl2, respectively.