The invention discloses a method for recovering neodymium iron boron trepanning oil sludge waste through a Ca-chloride reduction diffusion technology, and belongs to the technical field of recycling of rare-earth permanent-magnet industrial solid waste. The method includes the technological processes of drying of the oil sludge waste containing sintered neodymium iron boron, Ca-chloride reductiondiffusion, low-temperature soaking and calcium removal, doping of rare-earth-rich alloy powder, sintering, heat treatment and the like. The neodymium iron boron trepanning oil sludge waste serves as araw material, Ca-KCl is used for direct reduction diffusion to obtain regenerated neodymium iron boron magnetic powder, the powder is recycled, and a regenerated sintered magnet is prepared through the sintering technology. In the method, potassium chloride serves as a low-melting-point auxiliary agent so that the reaction temperature can be reduced, the reaction time can be shortened, the recycling rate is increased, and the use amount of metal calcium is reduced. Low-temperature calcium removal is adopted, the powder can be prevented from being oxidized, and the calcium removal efficiency is improved. By using the rare-earth-rich alloy, rare earth can be supplemented, and component adjustment and industrial production are facilitated. According to the method, the purposes of shorteningthe recycling technology, reducing the recycling cost, reducing the environmental burden and increasing the waste utilization rate are achieved.