Abstract: Residual stress is a key factor that directly affects fatigue, stress corrosion, fretting wear and other performance of engineering materials and components. However, it is difficult to accurately obtain the distribution of the deep residual stress field of the components using theoretical analysis and traditional non-destructive testing methods, which greatly hinders the development of advanced components. Due to the high penetration ability of thermal neutrons, neutron diffraction is an excellent engineering tool for providing mapping of residual stresses nondestructively in bulk components. Therefore, neutron diffraction was the most suitable non-destructive technique to characterize the deep residual stresses distribution. Therefore, National Important Project on Scientific Instrument and Equipment “the Neutron Diffractometer for Residual Stress and Defect in Materials and Components” was funded to built Engineering and Scientific Stress Diffractometer at China Advanced Research Reactor (CARR), which will serve the development of national important equipments, provide testing technique for manufacturing process of large-scale component and accumulate technical data for new material design. In order to fully play the role of Engineering and Scientific Stress Diffractometer in residual stress characterization of the engineering components, the mostly used crystal planes and the required wavelength for diffraction angle of about 90° of steel, nickel, copper, aluminum and titanium were analyzed. Thus, the optimal wavelength of the diffractometer was chosen to be around 0.164 nm, which satisfies the residual stress measurement for most commonly used metal materials. With this wavelength, the error of Fe(211) diffraction peak position was used as figure of Merit for the optics optimization. Optimized optics was obtained by tuning the horizontal and vertical focusing parameters. The neutron flux at the sample position that measured at the optimized optics with wavelength of 0.164 nm is a key parameter for the intensity performance of diffractometer. The activation method is the most commonly used technique to measure the distribution of neutron flux, which has the advantages of flexibility, adaptability, wide sensitivity and small disturbance to neutron field. In this work, the neutron flux at the sample is 3.0×10⁷ cm⁻²·s⁻¹ (±4.5%) at full reactor power of 60 MW. The resolution at the diffraction angle of about 90° is 0.42% by analyzing Fe(211) diffraction peak. The position resolution of the area detector was tested using a cadmium plate with three slit with known size. The horizontal position resolution is (1.44±0.03) mm. In this work, the optical optimization and performance calibration of Engineering and Scientific Stress Diffractometer at CARR were completed, which provides an experimental foundation for the instrument operation.