Structure of Cu-Sb melts has been studied by ab initio molecular dynamics simulations, high-temperature X-ray diffraction and resistivity measurements. Over the whole concentration range, heterogeneous coordination numbers are larger than that of homogeneous atoms. This indicates preferential Cu-Sb coordination in Cu-Sb melts. A drop is observed in maximum position of simulated Sb-Sb partial distribution functions around Cu75Sb25, which reveals the rapid increase of Sb-Sb coordination. Around eutectic melts, main peak splitting is observed in both structure factor and simulated total pair distribution functions, which reveals the co-existence of Cu-Sb heterogeneous and Sb-Sb clusters. Abnormal changes in temperature coefficient of resistivity are observed around pure Sb and in compound-forming range, which are well interpreted as reinforcement of Peierls distortion and Cu3Sb compound clusters, respectively. Structural inhomogeneity that results from atomic size effect also has been discussed by analyzing concentration dependence of Warren-Cowley parameters and concentration correlation functions.