In order to study the characteristics of spectral radiance measured by imaging spectrometer with motion compensation, the relationship between measured radiance and the tilt angle of the axis of Instantaneous Field of View (IFOV) was derived. In the Visible-near Infrared (VNIR) (0.4~1.0 μm), the ratio of the spectral radiance measured by imaging spectrometer with a certain tilt angle α to that with tilt angle α=0o (corresponding to observing nadir point) was calculated. Compared with observing nadir point (tilt angle α=0o), the measured total radiance decreases with the tilt angle α increasing in the process of motion compensation. And the proportion of measured target radiance in measured total radiance also becomes small. In order to make the increment of measured radiance keep or approach the gain by design in the process of motion compensation, the tilt angle of axis of α should be less than 30o.