In order to improve the flame retardant properties of polyester and solve the phenomenon of droplets of polyester fabrics, the coating liquid was prepared by blending graphene microcapsules with sodium alginate, and the coating polyester fabric was prepared by dip rolling method. The flame retardant properties, mechanical properties and thermal properties of the coated polyester fabric were examined, and the results showed that the limit oxygen index of the polyester fabric after the 25g/L sodium alginate and 1g graphene microcapsule flame retardant coating was increased from 19.7% to 28.34%, reaching the standard of flame retardant fabric. The finished polyester fabric reaches the V-0 standard, and the phenomenon of droplets of polyester disappears. The breaking strength of the fabric was reduced from 135.21N to 106.77N. Before and after the coating treatment, the temperature at which the fabric reaches the maximum thermal decomposition rate does not change significantly, the residual carbon rate increases from 12.07% to 26.98%, and the maximum mass loss rate decreases from 1.79%/°C to 0.96%/°C. At the same time, the enthalpy value of the polyester fabric before and after finishing increased from 58.4J/g to 68.4J/g. The thermal conductivity of the fabric was increased from 0.587 W/cm.°C× 10-4 to 0.842W/cm.°C×10-4, and the thermal properties were fully improved. The residual carbon formed after the fabric is burned from none to continuous and dense.