Multicomponent Ni7Co3 alloy-Au nanorings can be facilely synthesized at room temperature using metallic Ni7Co3 alloy nanorings as both reducing agent and sacrificial template in water. These novel alloy-Au hybrid nanorings are well biocompatible due to coating with poly(vinylpyrrolidone) and gold nanoparticles. When increasing the molar ratio of alloy to gold salt from 1:1 to 5:1, the number of the gold nanoparticles loaded on the surface of alloy nanorings were found to be decreased, and their morphology was transformed from rod to particle, remaining the ring-like assemblies. Their saturation magnetization increased due to the ring-like assemblies, resulting in the enhancement of the signal intensity in Spin-spin relaxation time (T-2) weighted magnetic resonance imaging measurement. These alloy-Au hybrid nanocomposites can perform as multimodal imaging contrast agents for cancer cell diagnosis by two-photon fluorescent imaging and T-2-weighted magnetic resonance imaging. In addition, their potential application for photothermal therapy was preliminarily investigated.