The invention provides a single-phase AB4 type superlattice hydrogen storage alloy electrode material. The chemical composition of the single-phase AB4 type superlattice hydrogen storage alloy electrode material is La1-xMgx(NiAly)z, wherein x, y and z represent molar ratio; the numerical ranges of x, y and z are as follows: x is greater than or equal to 0.20 and is less than or equal to 0.24; y is greater than or equal to 0.021 and is less than or equal to 0.034; z is greater than or equal to 3.70 and is less than or equal to 3.93. The single-phase AB4 type superlattice hydrogen storage alloy electrode material is of a single-phase AB4 type superlattice structure; the space group is R-3m; the phase peakness is 100wt.%; a preparation method of the single-phase AB4 type superlattice lanthanum-magnesium-nickel-aluminum hydrogen storage alloy electrode material mainly comprises the following steps: putting alloy ingots into a stainless steel annealing pot with resistance to high temperature, controlling the ratio of the volume of the alloy to the volume of the annealing pot to be 2 to 3, then sealing the annealing pot by using a graphite sealing gasket, and putting the annealing pot in a vacuum annealing furnace for carrying out annealing treatment. The preparation method of the single-phase AB4 type superlattice hydrogen storage alloy electrode material is simple in operation and equipment; the process conditions are stable and easily controllable; the industrial production and application can be facilitated; the prepared single-phase AB4 type superlattice alloy can be directly used as nickel/metal hydride battery negative material; the alloy has the characteristics of high discharging capacity, long cycle life and low cost.