The object of our study is the biggest island of the lake Baikal, which is a natural area of preferential protection of federal significance, and it is a part of the Baikal National Park. In the present paper, the authors assessed ecological and geochemical state of the soil cover of the Olkhon areas exposed in the past to the agricaltural impact. Study of grassland and steppe geosystems on the island was performed by key-site method for the first revealing indicator elements in the soil cover. Trace elements concerning to I-III classes of hazard were used as the indicators: As, Hg, Pb, Zn, F (high hazardous), Co, Ni, Cu, Cr (moderately hazardous), and Ba, V, Mn, Sr (low-hazard). The determination of Hg and As was carried out by atomic absorption spectrometry (AAS), and other elements were detected by X-ray fluorescence (XRF). It was shown that the concentrations of F, V, Mn, Co, Cu, Zn, Ba, Hg are high relatively to the Clark, the Cr and As contents are less than the Clark, the Ni content is close to the Clark, and concentrations of F, V, Zn, Pb are higher than the region background. This is a geochemical feature of the studied soils of the Olhkon island, which were formed by magmatic and metamorphic rocks. The obtained analytical and geochemical data indicate that the studied territory can be attributed to a quite satisfactory and considered as a background in the process of the further ecological-geochemical assessment of the former agricaltural lands on the Olhkon island.