Comparing to the linear scanning space camera in low satellite orbit，images captured by the area array staring imaging system in geostationary orbit usually emerges more blur because of the satellite vibration in the relative longer exposure time. To eliminate the motion blur degradation, the paper proposed to capture multiple short-exposure images and fused them on sub-pixel scale instead. The imaging system in geostationary orbit includes the feature of staring at the same area for a long time. Therefore the task mode of time-sharing short-exposure could get multiple less blurred images of the same area. Next, the sub-pixel displacements between the different frames are estimated by image registration algorithm with 0.1 pixel accuracy. And then, the images are fused to improve the low signal-to-noise ratio because of the short-exposure. Excellent results have been obtained by the sub-pixel image registration and image fusion in the paper.