As a wide spectral range and high resolution infrared spectroradiometer based on linear variable filters has been developed, a new sub-region multi-point calibration method is proposed. Its calibration principle is as follows. First, divide the target temperature region into n sub-regions, measure and record the infrared spectroradiometer data corresponding to n+1 blackbodies with different temperatures in the target region, and calculate the calibration coefficient for each sub-region. During the measurement of an unknown radiation spectrum, compare the blackbody spectra previously measured at calibration temperatures in order to find the proper sub-region. Use the corresponding calibration coefficient for calibration in order to improve measurement accuracy. We use this calibration method to calibrate a self-developed linear variable filter-based spectroradiometer and inverse the blackbody temperature error according to calibration results. The experiment results show that the calibration accuracy better than 1.5 K is achieved, and the proposed method can be used for radiometric calibration of infrared spectroradiometers.