By means of proteolysis with trypsin and subtilisin,in the cell wall of Candida utilis, a major structural cell wall protein with molecular mass of 33 ku was found.The 33 ku protein was quite different from most of the other cell wall proteins in Candida utilis. In cell wall it was not hydrolysed by trypsin, but was sensitive to subtilisin. The 33 ku protein was found to exist in cell wall of all logarithmic growth phases. Especially in early logarithmic growth phase, it was proved to be the only protein that was not sensitive to trypsin. The result demonstrated that this protein was important for connection of cell wall skeleton components-glucan, and for the intact structure of cell wall. It was an important integral cell wall protein.