The protein desorption of human serum albumin and human fibrinogen from the surface of poly(3-hydroxybutyrate) films was studied using ATR-FTIR spectroscopy. The diffusion model for reversible and irreversible sandwiched layers was confirmed. The reversible ratio (ratio of reversible adsorbed concentration to irreversible adsorbed concentration as a function of time allows for a suggestion as to a kinetic model of the initial stage of thromb formation. The parameters of adsorption/desorption for both proteins are compared. The reversible ratio of plasma protein adsorption is proposed as a quantitative criterion of thromb-resistance behavior for polymers in biomedicine; namely, controlled drug release vehicles, artificial vessels, magistrals, reservoirs for blood storage, and surgical threads, especially. The mechanism of interaction of protein molecules with poly(3hydroxybutyrate (PHB) macromolecules is discussed.