The invention discloses a method for recovering nickel from calcium and magnesium slag containing nickel through a transformation solution. The method mainly comprises the steps of preparation of the transformation solution, transforming, filtering, washing, increasing of the concentration of nickel in filtrate, detection of the filtrate, replacement and recovery of the nickel, and the like. The method has the advantages that provided raw materials are cheap, the process and technique are simple, the reaction is mild, operation is easy and convenient, and large-scale production can be achieved easily; in addition, no environment pollution is caused in the recovery process, and the method accords with the national environmental protection policy; meanwhile, the substance Na3AlF6 which is obtained after transformation and is more difficult to dissolve can serve as a fluxing agent of electrolytic aluminum, obtained nickel chloride recovery liquid can serve as the raw material for producing ferronickel products after being used repeatedly, or Nis generated after Na2S recovery is conducted directly enters a pyrogenic process system, the production cost is reduced, and the comprehensive utilization level of resources is increased; and the method is perfectly combined with an existing nickel sulfate production technique, existing production is not affected, the process is simple, the production cost is low, and the environmental friendliness effect is good.