The effect of Antifreeze Protein Type I (AFP I, one type of fish antifreeze protein) on ice crystallization was examined quantitatively based on a "micro-sized ice nucleation" technique. It is found that Antifreeze Proteins can inhibit the ice nucleation process by adsorbing onto both the surface of ice nuclei and that of foreign dusts. This leads to an increase of the ice nucleation barrier and the desolvation kink kinetics barrier. Based on the latest nucleation model, the increases in the ice nucleation barrier and the kink kinetics barrier were measured. This enables us to quantitatively examine the antifreeze mechanism of AFP I.