The control of ice growth in ice slurry is important for many fields， including (a) the cooling of the brain during cardiac arrest， (b) the storage and transportation of fresh fish and fruits， and (c) the development of distributed air-conditioning systems. One of the promising methods for the control is to use a substance such as antifreeze protein. We have observed and report here growth states of ice particles in both quiescent and flowing aqueous solutions of winter flounder antifreeze proteins in mini-channels with a microscope. We also measured ice growth rates. Our aim was to improve the levels of ice growth inhibition by subjecting the antifreeze protein solution both to preheating and to concentrating by ultrafiltration. We have found that the ice growth inhibition by the antifreeze protein decreased in flowing solutions compared with that in quiescent solutions. In addition， unlike unidirectional freezing experiments， the preheating of the antifreeze protein solution reduced the ice growth inhibition properties. This is because the direction of flow， containing HPLC6 and its aggregates， to the ice particle surfaces can change as the ice particle grows， and thus the probability of interaction between HPLC6 and ice surfaces does not increase. In contrast to this， ultrafiltration after preheating the solution improved the ice growth inhibition. This may be due to the interaction between ice surfaces and many aggregates in the concentrates.