When it is applied to quantum image stitching, the traditional scale-invariant feature transform (SIFT) algorithm will result in the problems such as unreasonable feature point distribution and high mismatch rate. So an improved SIFT quantum image stitching algorithm based on dynamic threshold and global information is proposed. In the aspect of unreasonable feature point number, as the number is proportional to the number of quantum dots or quantum rings, the contrast threshold of SIFT algorithm is set by calculating the density of quantum dots or rings so as to get the appropriate feature point number. In the aspect of reducing high false mismatch rate, a global information descriptor is constructed and combined with the local SIFT descriptor. The experimental results show that the improved algorithm can effectively complete the stitching of quantum rings, quantum wire and quantum dot images, effectively control the feature points of quantum images within a reasonable range, and reduce the mismatch rate from 17.34%～33.02% to 10.84%～20%, which makes the quantum image stitching have better reliability.