<p>The invention discloses a purifying method of monoglycoside acid which comprises selective oxidizing primary hydroxy group of the monoglycoside, exchanging the reacted composite liquid through an activated strong acid cation exchange resin bed and then eluting the ion exchange bed through purified water as elution. The invention separates the monoglycoside acid from inorganic salt effectively, the separated monoglycoside acid can be directly applied to manufacture monoaldonic acid lactone.</p>
