Abstract: In order to verify the motion of braiding machine and predict the properties of the composite braided material,a method for braiding machine motion simulation and geometric modelling of the yarn braiding structure is proposed.A geometric modelling method is proposed for generating a tight braiding structure of yarns for the Maypole braiding which uses the geometric correspondence between the spatial state of the basic braiding unit and its plane expansion to obtain the direction field on the mandrel surface which is used for generating the yarn trajectory.A double-layer hexagonal braiding machine is studied and a method for generating braiding structure with correct topology is proposed.Proposed method creates yarn tension by alternating corner cutting operation and point deletion operation,and realizes collision detection between yarn and mandrel with the help of virtual yarns.Based on various evaluation strategies about yarn residence ratio,porosity and average weaving ratio,the simulation experiment on the mandrel models with various shapes verifies the effectiveness and robustness of the proposed method.