The basic principle of the field-widened achromatic,temperature-compensated wind imaging interferometer (FATWINDII) is introduced.By using the equivalent and the approximation methods,the expression of the system responsivity in FATWINDII is deduced.The system responsivity can be improved by increasing the Field of View (FOV) and the transmittance of the FATWINDII.According to the structural parameters and compensation scheme of the FATWINDII,the air-equivalent length is 14.4 cm and the system transmittance is about 0.42.According to the specifications of Charge-Coupled Device (CCD) and the structural parameters of the FATWINDII,the variations of the system responsivity with the FOV and the pixel numbers are given analytically and simulated numerically.It is presented that the actual sensitive area is one over sixteen of the CCD in the FATWINDII laboratory space-borne simulation experiments.The study provides a theoretical basis and practical guidance for the design,development,calibration and data post-processing of the space-borne FATWINDII.