The structures of [Ni70Co30(25Å)/Cu(20Å)20 multilayers were investigated by X-ray anomalous scattering technique. Different structural behaviors at the Cu/Ni70Co30 and Ni70Co30/Cu interfaces were obtained respectively. For the as-deposited sample, the interfaces are asymmetrical. An 8Å thick CuNi3 and a 4Å thick NiCo layers are observed at the Cu/Ni70Co30 interface, however the Ni70Co30/Cu interface is sharp. For the annealed sample, the sharp Ni70Co30/Cu interface is replaced by a CuNi2Co sublayer of about 12Å thick. The X-ray diffuse scattering experiments, performed with the incident X-ray energy close to the Co, Ni and Cu K edges respectively, show the distribution of Co, Ni and Cu at the interfaces is not uniform.