The invention relates to a method for preparing lightweight porous aluminum phosphate- quartz ceramic balls. The method is characterized in comprising the following steps: (1) silica powder, alumina powder, aluminum dihydrogen phosphate powder and frit powder are subjected to dry mixing according to a certain ratio; (2) granulation and molding are carried out, such that a cylindrical blank is prepared; (3) the blank is dried for 5h under a temperature of 70 DEG C, and is placed into an alumina crucible with a semispherical-shaped inner bottom; the blank heated to a temperature of 150 DEG C in an air atmosphere with a speed of 5 DEG C/min; the temperature is maintained for 2h; the blank is heated to a temperature of 380 DEG C with a speed of 10-20 DEG C/min, and the temperature is maintained for 1h; the blank is heated to a temperature of 680 DEG C with a speed of 1 DEG C/min, and the temperature is maintained for 2h; the blank is heated to a temperature of 1150 DEG C with a speed of 5 DEG C/min, and the temperature is maintained for 2h; and the product is naturally cooled to room temperature, such that the lightweight porous aluminum phosphate-quartz ceramic balls are obtained.