The present application relates to a thermal insulation fireproof cloth for power battery and its preparation method. A thermal insulation fireproof cloth for power battery includes a fireproof cloth made from fireproof fiber, which can include one or more layers. The fire-facing surface of the fireproof cloth is coated with a high-temperature-resistant fireproof inorganic coating, and an unexposed surface of the fireproof cloth is coated with a structure reinforcing coating. The fireproof cloth is made into a box shape matching with a battery pack and arranged between a battery cell and battery housing. The fireproof cloth is made of high-silica fiber fabric or alumina fiber fabric. The fireproof inorganic coating is an inorganic material coating including SiO2 and Al2O3. The structure reinforcing coating is a coating which contains PTFE, silane, phosphate and alumina.