In order to meet the needs of geostationary orbit high-resolution imaging and deep space astronomical observation, and on the basis of the rapid development of rocket carrying capacity, the caliber of space-based remote sensing cameras in China has developed by leaps and strides, from 1 m caliber to 3 m caliber and above. Wiffletree support structure is widely used in mirror assemblies with diameter of 2 m and above because of its uniform distribution of support points and strong deformation adaptability. However, due to the large number of support points and complex structural connection links of Wiffletree support structure, the traditional method of mirror assembly and positioning can not meet the needs of fast and accurate assembly. A multi-point joint positioning method based on the bidirectional limit of the optical machine was proposed. By completing the positioning assembly of the Wiffletree structure and the bearing plate of the camera in advance, and adjusting the relative position of the mirror and the bearing plate, the pointing accuracy of the mirror optical axis could meet the requirements. Finally, micro adjustment was made for each support point to ensure uniform bonding gap and minimum assembly stress. The method was applied to the installation and adjustment of a 3 m mirror assembly. The verification results show that the method has low stress and high efficiency, and can meet the requirements of the installation and adjustment of Wiffletree support structure of large aperture mirror.