Particles may break after multiple impacts even during low-velocity collisions. Breakage probability is one of the key factors affecting the particle fragmentation. To investigate the effect of particle size on breakage probability, 44 sets of repeated impact experiments were conducted using a new particle impact device. Marble spheres with different diameters were repeatedly impacted against three different kinds of target plates under different velocities. A total of 22,740 collision experiments were performed to obtain reliable statistical results, and the strength of the marble spheres with different diameters was also tested. The results indicate that there exists a threshold velocity that influences the size effect of the breakage probability. Above the threshold velocity, the breakage probability increases along with the increase in sphere diameter. However, below the threshold velocity, the breakage probability first increases and then decreases with the increase in sphere diameter. This special phenomenon is referred to as the "abnormal size effect". Subsequently, a two-parameter function was used to describe the relationship between the breakage probability and the number of impacts, and this function fits the experimental results well. The strength of the marble spheres declines as the sphere diameter increases, but the rate of the strength reduction decreases progressively with the increase in sphere diameter. The abnormal size effect can be explained using the sphere strength and the energy dissipation rate. (C) 2020 Elsevier B.V. All rights reserved.