Acetylation of $\varepsilon$-amino groups of lysines changed the conformation of glycinin isolated from soybean. Soy glycinin with lysine residues modifications of 0\%, 25\%, 65\% and 95\% were used for the experiment. Surface hydrophobicity was found to increase in about 3 times when lysine residues were excessively modified to above 95\%. Masking of charged lysine residues, exposure of hydrophobic interior and subunit dissociation should have contributed to the conformational change that can be detected by UV spectra and the change of the intensity of effectiveness of pH, salts, temperature and conglycinin aggregation or solubilization of glycinin. The effect of acetylation on solubility of protein was investigated. Solubility of glycinin was increased and isoelectric point was shifted to acidic region. Salts (NaCl, CaCl$_2$) were found to little affect solubility of acetylated glycinin in contrast to native one. Heat stability of acetylated glycinin was increased, conglycinin affected little on solubility of acetylated glycinin in contrast to native one.