The content of biologically active substances and the level of antioxidant activity in the aerial organs of different sexual forms of Sibiraea altaiensis (Laxm.) Schneid. during the growing season were investigated for the first time. It was found that the maximum content of biologically active compounds varies depending on the stage of development, plant organ and also gender. The amount of flavonols (5.69%), tannins (30.17%) is higher in the leaves of male plants during the budding of plants, catechins ‒ in inflorescences (0.61%) of female plants, pectins ‒ in male buds (1.54%), protopectins ‒ in the leaves of males (8.99%) in the budding phase and in the leaves of females (9.62%) in the fruiting phase of plants and carotenoids ‒ in the leaves of males (70.6 mg%) and female (61.86 mg%) plants in the fruiting phase. Stalks of S. altaiensis contain quite a high amount of tannins (20.1%), pectins (1.49%), protopectins (5.93%) and carotenoids (17.37 mg%). The highest (antioxidant activity) AOA was detected in water (2.03 mg/g) and water-ethanol (1.75 mg/g) extracts from the leaves of male S. altaiensis plants. The AOA of water and water-ethanol extracts from the aerial organs of S. altaiensis is authentically positively connected with the content of all the studied substances, except for pectins.