Laboratory spectral calibration research of a dispersive hyperspectral imager is investigated. During laboratory spectrum acquisition, the heat generated inside the imager leads to center wavelength shifts. Due to the narrow bandwidth of hyperspectral imager, spectrum shifts will affect radiometric calibration accuracy. As a result, a spectrum offset correction model is put forward to correct spectral calibration. Moreover, correction precision is analyzed and radiance of integrating sphere is simulated according to spectral calibration results before and after correction. Compared with real integrating sphere data, it is proved that the model can correct spectral shifts well.