Multispectral area CCD camera based on liquid crystal tunable filter (LCTF) is a new spectral imaging system, which could record image of one wavelength on the area CCD by utilizing electrically controlled birefringence of liquid-crystal and interference principle of polarized light. Because of the special working principle of LCTF and frame transfer area CCD, the existing radiometric calibration method can not meet the precision need of remote sensing application if it is used for LCTF-camera. An improved radiometric calibration method is proposed, in which the camera performance test and calibration experiment are carried out relying on the devices of integrating sphere and standard detector, and the absolute calibration coefficient is calculated via correcting frame transfer smear and improving data process algorithm. Then the validity of the laboratory calibration coefficient is checked by a field validation experiment. Experimental result indicates that the calibration coefficient is valid, and the radiation information on the ground could be accurately inverted from the calibrated image data. With the resolution of radiometric calibration of LCTF-camera and the improvement of calibration precision, the application field of the image data acquired by the camera would be extended effectively.