Abstract: To address the issue of difficulty in measuring the pulse parameters of current 100 GHz bandwidth optoelectronic devices, an electro-optic sampling system based on a cage structure was proposed. The working principle of the electro-optic sampling method was introduced, the technical difficulties of the full-space electro-optic sampling method were analyzed, and the optical path structure in a targeted manner was optimized. A cage structure was introduced to integrate the laser beam splitting node and the illumination optical path, and the fiber-space light hybrid transmission method was adopted to improve the stability of the system, reducing the beam drift from 12 μm to 2 μm, reducing the system volume by 85%, and increasing the assembly and adjustment efficiency by 70%. Finally, the system was used to test the pulse width parameters of a 100 GHz optoelectronic detector. The results show that the pulse parameters of 100 GHz optoelectronic devices can be tested, and the repeatability is good.