The invention discloses a new application of the antitumor effect of a Miao ethnomedicine psammosilene tunicoids, and simultaneously discloses a preparation method and preparation of the pharmaceutical part of psammosilene tunicoids with the antitumor activity. The preparation method mainly comprises the steps of: extracting by ethanol, concentrating, extracting by n-butyl alcohol, purifying by macroporous absorption resin, and the like to obtain the total saponins of psammosilene tunicoids (TSPT). The total saponins are used as raw materials to prepare clinical commonly used pharmaceutical preparations such as tablets, capsules, injections and the like. A method of pharmacodynamic evaluation both in vivo and in vitro is adopted, wherein shown by in vitro tests, the TSPT has stronger inhibitory actions on 6 tumor cells of stomach cancer, liver cancer, colon cancer, ovarian cancer, breast cancer and melanoma, but has unobvious inhibition on the normal splenic lymphocyte; shown by integral animal in vivo experimental results, the TSPT has an inhibition rate as high as 72% on S180 solid tumors and has high action valence, but has small influence on the body weight of mice; and compared with a positive drug cis-platinum, the TSPT has lower side effect. Shown by the experimental results, the TSPT has strong anticancer valence, low side effect and the advantage of original innovation.