A new acylated flavonol glycoside, kaempferol-3-O-β-d-(2-feruloylglucopyranosyl) (1 → 6)-[β-d-glucopyranosyl(1 → 2)]-β-d-glucopyranoside, named tangutorumoside A (1), together with 12 known compounds, was isolated from 50% acetone extract of Cardamine tangutorum. Their structures were elucidated by NMR and MS experiments. In addition, compound 1 could promote the proliferation of splenic lymphocytes and thymic lymphocytes with ConA in vitro.