Cryogel is a coprecipitate of a cell adhesion protein with human plasma proteins produced from patient plasma. Cryogel is insoluble at a low temperature (4°C), and it is soluble at a high temperature (37°C). The diseases producing cryogel are rheumatoid arthritis, thrombosis, and so on. Cryogel is a physical gel formed by the heterophilic aggregation of EDA (+) fibronectin (EDA (+) FN), plasma fibronectin (pFN), fiburinogen (Fbg), and heparin (Hep). EDA (+) FN is a cell adhesion protein that does not exist in the blood, pFN and Fbg are plasma proteins, and Hep is a glucosaminoglycan. In this report, we describe the interaction of the cryogel composition molecules, and the condition of cryogel formation. The binding constant (KA) is measured by surface plasmon resonance (SPR). The order of strength for the interaction was Fbg-Hep>EDA (+) FN-Hep>Fbg-Fbg>Fbg-EDA (+) FN>Hep-pFN>Fbg-pFN. Hep-EDA (+) FN affinity is about 70 times bigger than that of Hep-pFN. It is thought that cryogel formation is controlled by the balance between aggregation size and aggregation concentration. So, the most suitable gelation condition was examined from the diffusion coefficient of the aggregate and the amount of aggregate by the dynamic light scattering measurement and the turbidity measurement. It was found that the cryogel grew around the self-aggregate of Fbg from the temperature dependence of diffusion coefficient. The diffusion coefficient ratio at a low temperature (5°C) became 1/1000 by adding Hep and EDA (+) FN into Fbg. On the other hand, the amount of aggregate by the three-element Fbg-Hep-pFN was much more than that of Fbg-Hep-EDA (+) FN. In other words, an important factor is the ratio of EDA (+) FN to pFN for the cryogel formation. Aggregation occurred most efficiently at EDA (+) FN: pFN: Fbg: Hep=0.05: 0.95: 15: 1 (mol%). Cryogelation is thus the Fbg-pFN aggregations of plasma proteins crosslinked by EDA (+) FN-Hep aggregates.