The conditions of the pyrogenic factor manifestation in the dynamics of the geosystems of the Baikal basin were described with data of Prebaikalski national park (PNP). Special features of the territory study natural conditions were examined, including the climatic conditions of the appearance of the forest fire centers. The extent of flammable period is fixed since April until September, a maximum quantity of fires is noted in the period of spring-early summer drought, but large forest fire areas take place with the irregular summer droughts. Lower forest fires predominate in the mountain taiga geosystems prevailing within this territory. Data on the forest fires from 1978 year were examined. It was built and analyzed the electronic database of forest fires from 1995 till 2017 year with GIS using. For the analysis of local conditions, the centers of fires and the burnt areas in the vector form were combined with the layers of topographic basis, forest inventory information, the thematic materials and field studies of the Institute of Geography RAS SB, space remote data of the different years for this territory, among which most informative proved to be the synthesized images Landsat-ETM 2000 ̶ 2017.It is represented integral cartographical pattern in 1995 ̶ 2017 of data spatial distribution of forest fire areas where were revealed the most flammable sections. The burnt area analysis was carried out. Localization conditions for large and small forest fires were examined. The catastrophic consequences of forest fires under the mountain conditions are connected with the making more active of slope processes, the degradation of soils as a result the processes of forest cover recovery are inhibited. It is stated the formation of the stably long-term derived forest cover structure in the Baikal basin. During the period in question exposing to forest fires of integrally more than half of PNP area characterizes the decrease of the water-protection and of environment forming functions in the Central ecological zone of the lake Baikal connected with post fire changing of geosystem states. The need of applying the territorially differentiated fire-prevention measures is based.