In this chapter, we will show how C-S-H pore structure evolves under cyclic cryogenic attack. The cryogenic attack impacts on the pore structure of C-S-H were comprehensively evaluated by nitrogen adsorption measurement. With this technique, we extracted fruitful pore structure information, including pore size distribution, pore volume, specific surface area, segmented surface fractality and pore tortuosity. C-S-H gels with various chemical compositions were discussed here. The pore size distribution and pore volume were determined using the Brunauer–Emmett–Teller (BET) method and the density functional theory (DFT) approach. By using Dubinin-Radushkevich (DR) and DFT approaches, the micropore information was additionally obtained. Specific surface area was calculated using the BET approach, and the segmented surface fractal dimension was determined using the Frenkel-Halsey-Hill (FHH) model. In addition, the tortuosity was also computed using the CPSM model, which provided additional evidence to estimate the cryogenic attack's influence on the pore structure of C-S-H.