An object of the present invention is to provide novel saccharides, 3-.alpha.-glycosyl .alpha.,.alpha.-trehalose having a 3-.alpha.-glucosyl .alpha.,.alpha.-trehalose structure represented by the chemical formula 1 within their molecules, their preparation and use. The present invention attains the above object by providing 3-.alpha.-glycosyl .alpha.,.alpha.-trehaloses having a 3-.alpha.-glucosyl .alpha.,.alpha.-trehalose structure represented by the chemical formula 1 within their molecules, their preparation and use.O-.alpha.-D-Glcp-(1.fwdarw.3)-O-.alpha.-D-Glcp-(1.fwdarw.1)-.alpha.-D- -Glcp Chemical formula 1