Abstract: Hydrothermal carbonization (HTC) is an efficient and environmentally friendly method for the treatment of polyvinyl chloride (PVC), enabling the clean utilization of PVC. Based on the co-hydrothermal carbonization of PVC and empty fruit bunch (EFB), this study investigated the morphology and formation evolution law of spherical hydrochar, and revealed the effects of reaction temperature and stirring power on the morphology and formation of hydrochar. The results showed that the hydrochar exhibited a double-layer spherical structure: the outer layer was composed of EFB-derived hydrochar with loose pores, while the inner layer was composed of PVC-derived hydrochar with dense pores. Increasing the reaction temperature was beneficial to the melting of PVC and the hydrolysis reaction of EFB, which promoted the improvement of the sphericity and particle size of hydrochar. Enhancing the stirring power facilitated the dispersion of molten PVC droplets, contributing to the reduction of the particle size of spherical hydrochar. However, when the stirring power exceeded a critical value, demulsification occurred, leading to an increase in particle size and a sharp decrease in sphericity. This study provides theoretical support for the effective control of hydrochar particle size in industry as well as its development and application.