A fine layer structure in the Ni/C multilayer (3-4 nm/6-7 nm) is deposited by magnetic sputtering by combining soft X-ray resonant reflectivity curve at 4.48 nm and grazing incidence X-ray reflectivity (GIXR) curve at 0.14 nm. It is found that the thickness of Ni-on-C interface is much rougher than C-on-Ni interface. By analyzing the optical constants, it shows that the interface in the Ni/C multilayer that of system is a mixture of Ni and C atoms; the Ni and C in multilayer system have excellent stability, and no interlayer is formed.