The aim of this paper was to determine relation between population and country in the meaning of Sweden scientist Rudolf Kjellén. In the introduction population as an agent of power was determined. It is presented that it's necessary to use modern approach in a science of the country. The analysis of the case at Kjellén's biologistics conception at the country has been determined, too. Two sub-systems in relation to population agent at the country have been analyzed: demo-politics and socio-politics. It has been referred on actuality at Kjellén's ideas as well as on certain deficiencies at his ideas. Conclusion at this paper has been dedicated to wide influences at Kjellén's ideas.