The invention relates to a preparation method of a white fabric. The method is characterized by oxygen bleaching and whitening a fabric containing cotton, and comprises the steps of adding a one-bath-one-step method bleaching solution (prepared from 1 to 2g/L of penetrating agent, 1 to 2g/L of anti-creasing agent, 2 to 7 percent (owf) of scutching agent, 2 to 9 percent (owf) of 40 percent by weight caustic soda solution, and 3 to 6 percent (owf) of 30 percent by weight hydrogen peroxide solution) with pH being 10 to 11 into the fabric for oxygen bleaching, then adding a fluorescent whitening agent for whitening, heating at a constant heating rate to 80 to 90 DEG C, carrying out insulation treatment, and cleaning, neutralizing and setting to obtain the white fabric. According to the method,a step of removing hydrogen peroxide is saved, so that the process time can be greatly saved, the water consumption is reduced, and the emission of noxious substances is reduced; the prepared white fabric is free of acidity and less in storage color change, and has a pH value stabilized in an acceptability limit from 5.5 to 7.0, and the whiteness improved by 1 to 2 or more compared with a traditional process; when preparing the white fabric with the same whiteness, the dosage of the fluorescent whitening agent can be saved by 10 to 40 percent, so that the economic benefits of enterprises canbe greatly improved.