Abstract: The management of cleanliness and hygiene in pigsties is a key part of the work that affects the health status of pigs, the labor cost of pig farms and the treatment of manure. Currently, manual cleaning of pigsties is unfavorable to both breeders and pigs. On the one hand, the humidity and the concentrations of harmful gases such as ammonia and hydrogen sulfide inside pigsties are higher than those in outdoor environments. Breeders' long-term exposure to such an environment has an adverse impact on their physical health. Moreover, manual manure cleaning in pigsties requires high labor intensity and long working hours. On the other hand, manual manure cleaning activities are likely to cause stress to pigs, which is not conducive to animal welfare. Therefore, using manure cleaning robots to replace manual operations is an effective solution and also the future development trend. This paper, combined with the management mode of modern pig farms, combs through the research and application cases of relevant robots at home and abroad from three perspectives: the cleaning scene requirements and spatial operation logic of pig farms, the flushing of empty pig pens, the manure cleaning on the ground of pigsties with pigs present, and the cleaning of underground manure ditches. It analyzes the research progress of key technologies of pigsty cleaning robots in multiple aspects, including application scene characteristics, chassis types, driving methods, positioning and navigation as well as path planning, manure cleaning mechanisms, and manure identification. The pigsty empty pen flushing robot is used for cleaning the floor and pen facilities of pigsties after each batch of pigs is removed under the "all in and all out" management mode of large-scale pig farms. Classified according to the chassis type, it is divided into wheeled and tracked. Among them, the wheeled chassis, often combined with mechanical arms and high-pressure water guns, is predominantly used for flushing operations in the aisles of pigsties. The ground manure cleaning robot in pigsties with pigs is designed for daily cleaning of residual manure on the floor inside the pen or on the aisle of the confinement stalls. Therefore, it requires certain capabilities in accurate manure identification and positioning, navigation, and path planning. Meanwhile, due to the different types and materials of the slatted floors in pigsties, the effective manure cleaning methods mainly include the scraper and shovel type and the manure collection type. The underground manure ditch is characterized by its narrow space and dim lighting. Therefore, the underground manure ditch cleaning robot is adopted to replace manual cleaning and the frequently malfunctioning manure scraper system. Mainly using a tracked chassis combined with high-pressure water flushing and shovel operation methods, it regularly removes residual manure in the manure ditch to ensure a good air environment in the pigsty. Based on the current development characteristics of Chinese pigsties and the problems and deficiencies that need to be focused on in the research of cleaning robots, this paper puts forward suggestions. These include developing a specialized chassis that is lightweight, has excellent load-bearing and off-road capabilities, and is suitable for pigsty cleaning scenarios; researching and developing an independent environmental perception and operation path planning system; developing durable sensors that are resistant to moisture and corrosion and are suitable for the harsh environment of pigsties; establishing a digital collaborative management and control platform to realize the collaborative work of multiple intelligent agents such as pigsty cleaning robots; and researching and developing automated facilities that are complementary to cleaning robots. It is emphasized that the pen and pigsty cleaning robot should adhere to the concept of welfare and healthy breeding. These suggestions are aimed at promoting factory-based, unmanned, and welfare-oriented intelligent pig breeding.