Non-spherical particles have shown increasing importance in the simulation of discrete element methods. Bonded particle model (BPM) is often used to realize the inclusion of non-spherical particles into the calculation using spherical calculation methods. However, the traditional grid subdivision method shows low efficiency and high computational complexity in the face of particle clusters containing a large number of elemental spheres. In this paper, an improved contact detection algorithm for bonded particles based on multi-level grid and bounding box method is proposed. The algorithm treats unbroken or broken new dusters as a unit in the process of contact detection. The contact detection problem including dusters is split into two steps: a pre-detection between the bounding spheres in the primary grid and an accurate contact detection of the elemental spheres in the secondary grid. The hopper experiment and the comminution simulation show that the algorithm has high accuracy and the calculation results are in line with the actual situation. The numerical simulation results of multiple sets of comparisons show that the improved algorithm has higher computing speed than the traditional grid subdivision algorithm, especially when the particle distribution in the calculation domain is relatively loose, the number of particle clusters is large or the composition of the cluster is more complicated. (C) 2020 Elsevier B.V. All rights reserved.