As a new and developing medical imaging technique, the digital tomosynthesis imaging (DTS) can provide researchers with confidence to distinguish the overlapping lesion tissue and make exact lesion-localizing. DTS employs the filtered backprojection algorithm for its rapid reconstruction speed and high reconstruction quality and reconstructs a series of the coronal images. However, the digital tomosynthesis insufficient dataset causes the hat-like intensity drop in its filtered backprojection reconstructed images along the rotation axis. The cone angle impact on the digital tomosynthesis axial intensity drop is analyzed and a reciprocal-cosine weighted intensity correction is introduced. To validate the effect of the axial intensity drop correction method, a DTS system is designed and built up and the anthropomorphic breast phantom is reconstructed with the reciprocal-cosine weighted correction method under different cone angle respectively. The reconstruction results demonstrate that the correction method can effectively minimize the axial intensity drop in digital tomosynthesis reconstructed images.