Abstract: The pixel transfer function (PTF) for analyzing microscanning technology′s effect on spatial resolution is given based on the detailed analyses of the aliasing effect decreased by the microscanning technology. The analysis, calculation and discussion on PTF are carried out for two modes of microscanning (2×2，4×4). The result shows that the microscanning technology can increase the focal plane spatial resolution, decrease the image aliasing effectively and improve the imaging quality significantly for FPA thermal imager. It is pointed out that even if highspatialresolution imaging device is not available, high spatial resolution images can still be obtained with lowresolution imaging devices by utilizing the microscanning technology.