In this paper

according to the similarity of the process of evaluation in advance and the process of creatures’ evolution in nature

the concepts of system structure

schema of system structure and the matrix for schema of system environment are presented.An schema-based appraising decision model is established according to the adapting degree of system structure and schema of the system structure to the matrix for schema of the system environment

the appraising classification criterion is also formulated

and some theoretical analysis for the appraisal system is made.This model and method are applied to the evaluation of the ecological security for city

and by contrast with fuzzy comprehensive assessment

the superiority of the appraising model and method is indicated.