Abstract: Appropriate loss and deviation models for transonic axial compressors were selected from detailed investigation.By combining them with the blade row-by-blade row model,a quasi-one dimensional approach for calculating off-design performance of multi-stage axial compressors was developed.This approach was then combined with complex adjusting optimization algorithm.A new method was thus established for enlarging surge margin in multistage compressors using variable stator stagger setting.The methodology had been incorporated into computer program and validated using data from an eight-stage transonic axial compressor.Results have demonstrated that variable stator stagger setting is a powerful method to rematch stages and can be used to enlarge aerodynamic stability range of multi-stage compressors.Numerical results also show the effects of reflection coefficient α in complex adjusting optimization algorithm on optimizing results are apparent and α=1.15 seems best.