Paper mill sludge is difficult to be treated with the high disposal cost, which limits the sustainable development of papermaking industry. The traditional disposal methods are mainly landfill and incineration, however, landfill and incineration will cause secondary pollution to the environment. Therefore, developing environmentally-friendly disposal methods is a key issue for paper mill sludge disposal. Many scholars focused on the comprehensive utilization of papermaking sludge, such as anaerobic fermentation, aerobic composting and production of building materials. Based on the rich biomass content in paper mill sludge, developing paper mill sludge-based functional materials by certain modification methods for water treatment can achieve the goal of "treating waste with waste". It not only conforms to the environmental protection concept of sustainable development, but also provides a new idea for the comprehensive utilization of paper mill sludge. This paper reviewed the sources, properties, disposal methods and comprehensive utilization of paper mill sludge, research status and prospect of the utilization of cellulosic substances in papermaking sludge. This paper aims to provide some theoretical support for the sustainable development of the paper industry.