The invention discloses a method for preparing a cubic shape green luminescent material of lanthanum zirconate doped with cerium and terbium. The method comprises the following steps: dissolving lanthanum nitrate, cerium nitrate and terbium nitrate in deionized water according to the mole ratio and stirring; adding PVP into the solution, controlling the concentration of the mass percent of the PVP at 0.25-1% and stirring; adding zirconium acetate into the solution, controlling the mole number of the zirconium acetate and the mole number of the total rare earth cation to be equivalent, adding a sodium hydroxide solution drops by drops to obtain a white precipitate and controlling the pH value of the solution at 6-9; putting the solution into a high-pressure kettle, taking the filling degree at 80% and processing for 6-40 hours at 180-220 DEG C; and centrifugalizing and drying the processed solution to obtain the cubic shape green luminescent material of lanthanum zirconate doped with cerium and the terbium.