The invention discloses steroid saponin compounds and a preparation method and application thereof. The preparation method comprises the steps of: mixing polygonatum odoratum with an aqueous solutionof ethanol for extraction, performing filtration and concentration by using an ultra filtration membrane and nanofiltration membrane device, then performing adsorption by using a macroporous resin column, performing elution with an aqueous solution of ethanol, performing concentration and recycling of ethanol, and performing freeze drying or spray drying to obtain steroid saponin extract; separating the steroid saponin extract by using low-and-medium pressure liquid chromatography with an OSD column, performing gradient elution by using a methanol aqueous solution with a volume concentration of 10-100%, and performing purification by using a preparative RP-HPLC to obtain the eight steroid saponin compounds. The steroid saponin compounds can be applied to prepare drugs for treating, improving and/or preventing metabolic syndromes, metabolic diseases, metabolic disorder and liver cancers of sugar or fat, food functional additives or healthy food, and the preparation method has simple operation and is easy to industrialize and popularize.