Numerous detectors and the large time scale make non-uniformity correction （NUC） challenging for an infrared focal plane array. Typical calibration systems for infrared remote sensing systems block the full optical pupil and expose the sensor to an on-board calibration source （blackbody） and may also point to deep space as a calibration source. It is impractical （or expensive） to calibrate the high dynamic range remote sensing system with an on-orbit full aperture calibration source. This paper proposes and simulates an internal calibration system wherein a controllable internal calibration illumination is superimposed on the space imagery. The CICS-NUC method is applicable to the NUC when the calibration source adopts steady-state mode. After a comprehensive simulation analysis， an on-orbit NUC method based on the controllable internal calibration sources （CICS-NUC） is proposed using this type of calibrator. The proposed approach provides effective NUC without blocking the full optical pupil when the sensor stares at deep space. After executing the proposed NUC method， the non-uniformity of the evaluation image was reduced from an initial pre-correction value of 15.87% to a post-NUC value of 1.2%. The proposed approach has advantages of high efficiency， adaptability， and real-time processing. In addition， compared with the scheme of cutting a large extended blackbody into the imaging optical path， the simple structure and compact design of the internal calibration device reduce system costs.