A surface accuracy analysis model for the support structure of a hexagonal prism modular deployable antenna is proposed because of the large-scale， modular， and high-precision development trend of deployable antennas. The structural composition of the hexagonal modular deployable antenna is elaborated， and the topological rules of the hexagonal modular structure are analyzed. Based on the idea of equal envelope circles and the basic theory of robotics， two mathematical modeling methods of envelope circle， point-surface method and two-point method， are proposed， from which the mathematical model of the intersection point of the equal envelope circle and the mathematical model of the included angle of rib unit are established； the mathematical model for accuracy analysis of the shape surface of the support structure of a modular deployable antenna with a hexagonal prism is built. Finally， the model is verified using a combination of numerical simulations and experimental verifications. The simulation and experimental results show that the enveloping circle can closely fit on the spherical surface， and it is in good agreement with the spherical surface. In the numerical simulation model， the modules of the hexagonal prism are connected accurately. In the experiment， the absolute error of feature points is mainly distributed in 5 to 10 mm， the relative error is mainly concentrated in the range of 0.05% to 0.1%， and the absolute error of the rib unit angle is mostly distributed in the range of 0.05°to 0.1°. The deviation between the measured and the theoretical values is small， and the values are in good agreement. The proposed model can solve the spatial coordinates of all module connection points， which provides a theoretical basis for the analysis and research of the shape accuracy of multi-module deployable antennas.