 A gradient structure intumescent flame retardant coating of polyethylene amine phytic acid, PEI, PA, was constructed on cotton fabric through a facile layer by layer, LBL, assembly method, resulting in excellent flame retardancy with a LOI value over 40%. The LBL assembly process had minimal influence on the physical properties of cotton fabrics and the coated fabric exhibited good flame retardant washing durability. Thermographometric analysis revealed that PEI, PA flame retardant coating changed the thermal decomposition process and promoted char formation, while SEM images showed that it formed an intumescent flame retardant, IFR, char layer, indicating obvious IFR action. This research provides a simple LBL assembly method for developing high-efficiency flame retardant cotton fabric with good durability and physical properties. This article was authored by Xinhua Liu, Hai Long Liu, and Yin Chun Fang.