The invention discloses total oligose in cistanche deserticola and a preparation method and application thereof. In the total oligose in cistanche deserticola of the invention, the content of the contained total oligose is not less than 40 to 60 percent based on glucose (C6H12O6), and the content of galactitol (C6H1>O6) contained in the total oligose ranges from 0.0 to 25.0 percent. Used as drugsfor relaxing bowel, the total oligose in cistanche deserticola of the invention eliminates the complex purification process required by purifying the galactitol from the cistanche deserticola, leads to maximum utilization of drug resources of cistanche deserticola and enhances the drug effect, thus having the advantages of definite healing efficacy, few side-effects and large group of applicationpeople. Due to moderate bowel-relaxing effect, the total oligose in cistanche deserticola is especially suitable for the old, lying-in women or valetudinarians.