The invention discloses a preparation method for preparing environmental-friendly thermal insulation ceramsite, and relates to the technical field of ceramsite. The preparation method comprises the following steps that a polystyrene granule is added into an additive, the mixture is put into a machine model to be heated and foamed to form a sphere, wherein the diameter of the sphere is 1-60 mm, the sphere is put into a pelletizer, a gelatine powder, cellulose and a powdery inorganic hydraulic cementing material are added according to a production sequence for pelletizing, the wall thickness is up to more than 0.5 mm, classification is conducted according to different varieties, and the preparation of the thermal insulation ceramsite is completed after pelletizing and curing molding. The used raw materials are environmental-friendly and cheap, can be stored, and do not occupy a large area; and in addition, the thermal insulation effect is better than that of a traditional technology, sintering is not needed, the energy is saved, the preparation process of the raw materials is completed in a field at one time, and the production efficiency is improved.