The invention relates to a special gamma scanning measuring system for a hot chamber and an installation method of the system. The special gamma scanning measuring system for the hot chamber comprises a support, a guide cylinder, a shielding transmission container, a hanging cylinder, a collimator, an attenuation shielding block, a shielding body, a gap positioning block, a gap block, a shieldingbox, a y-direction travel mechanism, steel cables, an x-direction travel mechanism, a detection trolley, a control system and the like. The special gamma scanning measuring system disclosed by the invention has advantages of simple structure, convenience in installation and dismounting, and safety and reliability. On the premise of thoroughly taking redundant functions into consideration, the special gamma scanning measuring system meets gamma scanning measuring requirements, and meanwhile, different hanging cylinders can be exchanged, and thus the measuring requirements of bar-shaped fuel assemblies, pipe-shaped fuel assemblies and the like can be met. By adopting the structural design of the square hanging cylinders and square guide cylinders, a function of respectively measuring four surfaces of each square assembly can be realized. The special gamma scanning measuring system for the hot chamber prevents staffs from being radiated by gamma rays. Different attenuation shield blocks and different gap blocks are designed to meet the measurement of different types of fuel assemblies and the measurement of different accuracy requirements. The shielding box is designed to avoid outside interference.