Efficient neighbor retrieval method and system for wide grading discrete element particle system

The invention discloses an efficient neighbor retrieval method and system for a wide-grading discrete element particle system. The method comprises the following steps: grouping the wide-grading particle system according to the particle size from coarse to fine; constructing a spatial orthogonal grid under the granularity of each grain group from coarse to fine, and obtaining neighbor matrix representations of the coarse grain group and the fine grain group based on a matrix discrete element contact method; based on the duality of neighbor contact, obtaining a coarse grain group neighbor matrix representation of the fine grain group by the fine grain group neighbor contact pair of the coarse grain group; and on the basis of matrix merging, obtaining neighbor matrix representations of the particles of each particle group and all the particle groups. According to the invention, a unit particle size grouping and multi-grid method is adopted, pure matrix operation of neighbor search of the wide grading particle d