Echelle, which is highly appreciated due to its excellent properties in recent years, has the advantages of low groove density, wide blaze angle, high diffraction grades, wide spectral range, high dispersion ratio, and high spectral resolution. Diffraction efficiency and stray light coefficient which can express the quality of the echelle directly reflect the optical properties of the echelle. Thus, accurate measuring of the diffraction efficiency and stray light coefficient is the precondition for grating applications. Therefore, based on the diffraction theory of echelle, the paper creatively puts forward a thought of using one system measuring echelle diffraction efficiency and stray light coefficient. The system introduces a double-rail structure, possessing the advantages of simple and novel structure, multiple functions in one machine. Through theoretical analysis and calculation, the structural parameters of the detection system are determined. The results indicate that the system can be used to measure echelle diffraction efficiency with the spectral range from 190 to 1 100 nm, and the system can also be used to measure echelle stray light with the spectral range from 200 to 800 nm, achieving the purpose for measurement of diffraction efficiency and stray light in one system.