Disclosed is a method for recycling and processing nickel in a stainless steel pickling waste acid. The potential of hydrogen (pH) value of a mixed waste acid is adjusted to 3.5 to 4.5 by lime, hydrogen peroxide is added, a reaction is performed for 0.5 to 1 hour, then the pH value is adjusted again to 4.0 to 4.5 by the lime, then a flocculating agent is added to enter into a sedimentation tank to obtain a clear liquid and sludges, the clear liquid enters into a second reaction tank, the obtained sludges are subjected to a filter pressing to obtain a filter cake, the filter cake is subjected to a back washing by stainless steel factory workshop ground washing wastewater, and filter pressing water is transferred into the second reaction tank. The lime is added into the second reaction tank to adjust the pH value to 9.0 to 10.0, the flocculating agent is added, a formed solid-liquid mixture is transferred into a second sedimentation tank to be subjected to a solid-liquid separation, solids are subjected to the filter pressing to obtain a nickel mud, a sulfuric acid is added into a filter pressing liquor to adjust the pH of effluent to 7.0 to 8.0, and environmentally acceptable discharge can be achieved. By means of the method, the effective recycling of heavy metal nickel can be achieved, secondary pollutions are reduced, sludge qualities can be improved, and waste acid treatment emission requirements can be met.