To find a better way of pretreatment for electroless nickel planting on MgLi alloy. MgLi alloy was pickled by using three different processes: phosphoric acid solution, nitric acid solution, phosphoric acid, and nitric acid solution. MgLi alloy was activated by using three different processes: hydrofluoric acid, ammonium hydrogen fluoride solution, and phosphoric acid and Ammonium hydrogen fluoride solution. Electroless nickel planting on MgLi alloy has been finished after different activations. The specimen was analyzed after activation and after nickel plating using metallurgical microscope, SEM, EDS and XRD. The results show that the oxide layer on the surface of MgLi alloy has been completely dismissed during pickling by phosphoric acid and nitric acid solution, and the surface is glossy. A layer of magnesium fluoride is formed on the surface of the sample after each activation process. The nickelphosphorus alloy coating is formed, and the particles are uniform and arrange tight. The best process of pretreatment is phosphoric acid 2 mL/L, nitric acid solution 10 mL/L, sodium fluoride 1 g/L, and 530 s at room temperature for pickling; ammonium hydrogen fluoride 20 g/L, 13 min at room temperature for activation.