A uniform, monodispersed superfine cuprous oxide (Cu₂O) sphere with a mean diameter of 850 nm has been synthesized by solution reduction. The study reported the synthesis and thermal properties of Cu₂O/PP composites for the first time. The surface modification of the superfine Cu₂O sphere was carried out by using a silane coupling agent KH-570. Fourier-transform infrared (FTIR) spectroscopy and the thermogravimetric analysis (TGA) curve revealed that the Cu₂O had been successfully modified by silane coupling agent KH570. The scanning electron microscope (SEM) shows that the modified Cu₂O can be uniformly dispersed in the polypropylene (PP) matrix, because through surface modification, there are some active functional groups on its surface, such as the ester group, which improves its compatibility with the PP matrix. The thermal stability of Cu₂O/PP composites was improved by adding a small amount of Cu₂O (1 wt % of PP). Therefore, based on the potential bacteriostasis of cuprous oxide, the low cost of PP and the results of this study, it is predicted that Cu₂O/PP composites can be used in infant preparation (such as milk bottles) with low cost and good thermal stability in the near future.