The invention discloses a preparing technology for an agaricus bisporus culture medium. Rotten hardwood leaves, pleurotus eryngii dregs and shii-take dregs serve as raw materials, and lime and gypsum serve as auxiliary materials. The preparing technology includes the following steps that 1, the hardwood leaves falling to the ground are collected and are exposed in the sun to remove parts of infectious microbes and parts of injurious insects; 2, the exposed leaves are soaked in lime water of 2% for 12 h and taken out; 3, waste material collection is carried out, wherein normal mushroom-harvested pleurotus-eryngii and shii-take bags without infectious microbe pollution are selected and removed, and dregs are uniformly collected; 4, waste materials are smashed, wherein the pleurotus eryngii dregs and the shii-take dregs obtained after bag removing are dried in the sun and then smashed into particles with the diameter of 0.3-0.6 cm; 5, piling is carried out, wherein the materials are mixed and piled, the pile comprises a layer of the pleurotus eryngii dregs with the thickness of 3 cm, a layer of the leaves with the thickness of 2 cm and a layer of the shii-take dregs with the thickness of 3 cm, watering is carried out every time one layer is piled till water flows out of the pile, the width of the pile is 1.5-2 m, and the height of the pile is 1.5 m; 6, first-time fermentation is carried out; 7, second-time fermentation is carried out; 8, inoculating is carried out.