Abstract:This paper sums up the concept of ecological security. It can be divided into four kinds according to the understanding of "ecology": (1) the concept that emphasizes the relation with sustainable development of each other; (2) the concept that emphasizes the meaning of eco-environment, (3) the concept that emphasizes environmental security, (4) the concept that emphasizes multiple ecosystems. The limitations of the assessment based on Pressure-State-Response (P-S-R) are: the scarce security trend, the scarce spatial difference, the scarce mechanism and practice. People pay more attention to the ecological security evolvement trend. The security factors are dangers that are to be triggered or accumulated under certain conditions. Security states will evolve even mutate because of the dangers. Ecological security from beginnings is threatened by all kinds of dangers. The danger factors span regional boundary, which lead to the spatial differences of ecological security. So, ecological security is a spatial concept. Regional ecological security means that the existing state and evolving probability should prevent human ecological security space from the harm of dangers factors that are caused by nature and human activity. It is not enough to explain and analyze ecological security based on the mechanism of pressure-state-response. In depth research and assessment system is necessary for perfecting ecological security theory and directing practice. The aspects that should be developed are suggested in the paper, they are: the especial ecological security mechanism of different regions; dangers research; the evolvement trend forecast; early warning system.