In order to improve the flame retardant properties of polyester (PET) fabrics, graphene aerogel (GA) flame retardant PET fabrics were prepared by hydrothermal reduction self-assembly method. Scanning electron microscopy was used to analyze the microstructure of GA, and the construction process parameters were discussed to optimize its structure. The effects of GA structure on the flame retardancy of PET fabrics were analyzed by limiting oxygen index (LOI) and cone calorimeter. The results showed that, the optimal preparation process conditions for GA/PET fabrics are as follows: the concentration of graphene oxide (GO) was 5 mg/mL, the ratio of GO to ascorbic acid was 1 to 6, and the reduction temperature was 100 ℃. When the GA content was 26.3%, the LOI value of GA/PET fabrics was as high as 32.1%, reaching the level of flame-retardant material, and smoke suppression effect achieved. It can be used as a new type of carbon material in the field of flame-retardant fabrics.