The niche ecostate-ecorole theory and niche expansion hypothesis were developed inthis paper. Each biological unit from individual to biosphere exits in a certain ecostate and hasits own ecorole in the environment. The "ecostate" of the biological unit is the accumiated re-sult of growth and development, learning, socio-economical development and the interactingwith surrounding environment in the past. The "ecorole" are the current effects on the envi-ronments, such as the rate of energy and matter exchange...