In order to reduce the inconsistency of spectral radiance caused by the aiming area differences between different spectroradiometers, the influence of field of view (FOV) angle and positioning on measurement accuracy was discussed. By establishing the spectral radiance measurement model of sunlight whiteboard and tungsten halogen lamp whiteboard, the differences between the average radiance and central radiance in the field of view of different geometric optical paths were analyzed. Numerical simulation shows that the correction factor of sunlight whiteboard path is only related to the size of FOV angle, while that of tungsten halogen lamp whiteboard path decreases with the increases of the measurement distance. When the distance is 600 mm, the correction factor of 8° and 14° FOV angle changes to 0.993 5 and 0.980 2, respectively. Finally, the experiment verified the influence of the angle error and displacement error on spectral radiance when using the tungsten halogen lamp whiteboard system. The results show that the correction factor presents asymmetry to the horizontal angle error and displacement error, and the difference between the two sides is as high as 2%. Therefore, the measurement results can be corrected according to the FOV angle and geometric positioning, which helps to improve the uncertainty level of spectral radiance measurement.