The invention belongs to the field of natural drugs, and particularly relates to a gypsophila oldhamiana Miq extractive preparation method and application. The gypsophila oldhamiana Miq extractive preparation method comprises the following steps that (a) gypsophila oldhamiana Miq dry roots serve as raw materials, are extracted in an ethanol refluxing mode, then pass through a macroporous resin column and is subjected to gradient elution through an ethanol-water system, 40-70% of ethanol eluant is combined, and gypsophila oldhamiana Miq total saponins are obtained; (b) gypsophila oldhamiana Miq extractive is obtained in the mode that the gypsophila oldhamiana Miq total saponins obtained in the step (a) is subjected to alkaline hydrolysis and pass through the macroporous resin column. A large amount of total saponins which do not have antitumor activity or are weak in activity in the gypsophila oldhamiana Miq dry roots are converted into the extractive high in antitumor activity through alkaline hydrolysis. A pharmacological experiment shows that the gypsophila oldhamiana Miq extractive prepared through the preparation method has superior antitumor activity.