The invention relates to a preparation method of a textile with a flame-retarding coating. The preparation method comprises the following steps: providing graphene oxide hydrosol with the concentration of 8.5mg/mL to 17.5mg/mL; uniformly mixing montmorillonite and water to obtain a montmorillonite suspension solution; uniformly mixing the montmorillonite suspension solution, the graphene oxide hydrosol and a thickener, so as to obtain a graphene oxide doped montmorillonite coating agent; coating the graphene oxide doped montmorillonite coating agent on the surface of the textile, so as to obtain the textile with the flame-retarding coating. A synthesis process of the graphene oxide doped montmorillonite coating agent provided by the invention is simple and easy to operate, is green and environmentally-friendly and is suitable for large-batch production. A coating finishing method is adopted and the coating agent is coated on the surface of the textile, so that on one hand, an excellent flame-retarding performance of graphene oxide and the montmorillonite can be sufficiently realized; on the other hand, the flame-retarding performance of the finished textile can be extremely improved.