According to the imaging gaps caused by scrolling imaging in the conventional assembled focal plane for a push-broom camera, a mechanical assembling method with uneven overlapping pixels was proposed. Firstly, a model was established to simulate the imaging process when the camera was scrolled. Then, the reason that the gaps appear was analyzed, and a mathematical formula for the gaps between the CCD viewing fields at a certain scrolling angle was derived. Accordingly, the allowable minimum quantity of the overlapping pixels between every two CCDs was derived as well. On these bases, a function of overlapping pixels of images was given for subsequent software programs to eliminate the superfluous pixels and to realize the gapless assembly. Analysis indicates that the error ε of this assembling method is less than one pixel, which satisfies |ε/D|<1. Finally, an example was given.