An airborne infrared multispectral scanner can image remotely both in downward-looking and side-looking modes, by solving the contradiction among spectral resolution, high spatial resolution and large FOV imaging with whole device whiskbroom working mode. A theoretical accuracy of the object positioning error can be acquired by simulating the imaging geometry, which indicates that the angle measuring accuracy of the infrared multispectral scanner is the main error source, and should be precise enough to guarantee the linear whisk broom stripe images′ pixel-level mosaic accuracy. Subsequently, a method of angular error compensation was adopted to reduce the long term and short term error. After compensation, the angle precision was ten times higher than before through labrotary test, and the accuray remained stable by environmental test. Also, the airborne flight test verifies the effectiveness of the compensation technology, the image relative geometric positioning accuracy is less than one pixel(10″), which can meet the requirements of image mosaic.