The invention discloses a heat-insulating film and a preparation method. The invention provides an excellent heat-insulating film which can meet an optimal heat-insulating effect of heat radiation. The heat-insulating film comprises three layers from top to bottom, namely, a film protection layer, a use layer and a release layer, wherein the use layer comprises a metal hardening layer, an upper transparent film, a glue layer, a lower transparent film, a metal oxide layer and an adhesive layer from top to bottom; the film protection layer comprises a protection base film and a protection adhesive layer from top to bottom. As two layers of PET base materials are bonded together, the heat-insulating film is relatively good in elasticity vibration absorption function and good in acute impact resistance, and the result of an impact test of a 500g testing ball at the height of 100cm shows that a piece of glass needing heat insulation can be effectively prevented from collision damage.