For transmission towers in service with long operation time or expansion and reconstruction requirements, the insufficient bearing capacity of some components leads to the failure of transmission towers to meet higher design requirements. Therefore, it is necessary to carry out reinforcement measures of Angle steel components to effectively improve the bearing capacity of transmission towers. Taking the typical Angle steel of transmission tower as the research object, the method of non-destructive reinforcement of transmission tower is put forward. The method uses bolts and fixtures to form the original member and the strengthened member into the combined strengthening member. The combined member does not need to cause damage to the original member, and has a simple construction and advanced applicability. A fine numerical model of composite components was established, and the effects of slenderness ratio of original components, fixture spacing (number) and steel properties on the reinforcement effect of composite components were studied. The calculation method of bearing capacity of composite components was deduced. The results show that the effectiveness of the proposed reinforcement method is remarkable, and the maximum reinforcement level reaches 56.34%. The slenderness ratio of the original component has a significant effect on the improvement level of the composite component, and the improvement effect of the composite component is gradually significant with the increase of the slenderness ratio of the original component. When the number of fixtures is an odd number and the distance between fixtures is less than 750mm, the reinforcement effect of composite components is the best. The steel properties of reinforced members have little influence on the bearing capacity and ductility of composite members. The method for calculating the bearing capacity of composite members is in good agreement with the finite element simulation, which can provide a reference for the design of nondestructive reinforcement of Angle steel of transmission towers.