The packed-bed latent thermal energy storage system (PLTES) is the key to ensuring stable and effective energy output in the process of resource utilization. It has great application prospects due to the development of packed-bed design and phase change material (PCM) encapsulation. PLTES system filled with encapsulated PCM spherical capsules is considered to be one of the most popular devices in scientific research and industrial applications because of its high charging and discharging rate and simple structure. This paper reviews the performance research of the PLTES system with spherical PCM capsules (PLTES-SC), including numerical simulation and application, and focuses on the features and approaches of optimal design. The main purpose of this paper is to introduce the necessary information of each technique and to promote further research on this type of device. First, the basic information, working principle, and design aspects of the PLTES-SC system are discussed, especially the spherical PCM capsules and heat storage tank. And then, the numerical research on the heat transfer performance of the PLTES-SC system is reviewed. In addition, the emphasis of the work has been placed on the optimization methods of the system thermal performance, including the shape of the spherical capsule, the packing method, the structure design of the tank, and the operation strategy of the whole system. Finally, various practical applications of the PLTES-SC system are reviewed.