Abstract: The carrying capacity of resources and environment is a key element which needs to be considered in economic and social development planning. Quantitative assessment of it has become one of the frontiers of earth science research. The concept, principle, method and criteria of carrying capacity assessment need to be explored further. In this paper, the authors established a new theory and some key techniques to assess the carrying capacity of geological environment, using multi-disciplinary approaches based on risk theory, functional theories of production-life-ecology, geological environmental theory, marginal theory and some other means. On the basis of the risk theory and with the prerequisite that if the life, property and health risk which originate from human activities such as producing and livelihood can be accepted as an entry point and link, the authors proposed the concept of allowable and ultimate carrying capacity, and classified the status of carrying capacity into three levels:safely carrying, allowable over-carrying and unacceptable over-carrying. Risk-based evaluation of the geological environment carrying capacity generally includes four steps:determination of the scope of the research; identification of the environmental geological problems; evaluation of the individual factors related to life, property and health risks; integrating the individual factor evaluations into a comprehensive evaluation of the current and predicted carrying capacities. This approach can support the decision making on identifying the "three red lines" of national terrestrial development.