Based on the proposed basic mechanical hypothesis and calculation analytical model of unidirectional stiff ener composite panel unit, a method was developed for analyzing structure efficiency quickly under the multi-con- straint case. Analysis and optimization of structure efficiency for typical unidirectional stiffener composite panel was done using present method. And the structure efficiency variation trend which changes with the design parameters was obtained as well as the relatively optimum structure parameters. Present method synthetically accounts for the global stability of stiffener, local stability, static strength constrains of structure and interaction of them. Upon the basic hypothesis, the discrete variables of composite structure change to independent continuous design variables, thus it can observably simplify the analysis of structure mechanical properties and optimization. Results from the test and finite element analysis were compared with those from the present method, and they exhibit in good agree- ments. The research results can directly provide reference for the design of the unidirectional stiffener composite panels. And the method has good practical engineering application and reference value.