A method of preparing a fabric for perspiration exhaust pajamas and underclothing includes the following steps: (1) grey cloth weaving: weaving a perspiration exhaust fiber, a regenerated cellulose fiber, and spandex into a grey cloth; (2) singeing: singeing the grey cloth to obtain a singed grey cloth through a two-face-two-back singeing; and (3) moisture adsorption and perspiration exhaust finishing: immersing the singed grey cloth in a finishing liquid, taking out the singed grey cloth for drying, baking, washing, and then drying to a constant weight to obtain the fabric for perspiration exhaust pajamas and underclothing.