Low-permeability conglomerate reservoirs are characterized by strong heterogeneity，small pore throat radius，and complex mineral components. In water injection development of the reservoirs，the content and particle size of suspended solids in reinjection water are main factors leading to reservoir damage. However，the recommended indicators of injection water quality for low-permeability clastic reservoirs are unsuitable for conglomerate reservoirs. Therefore，injection water quality indicators for low-permeability conglomerate reservoirs should be formulated based on the characteristics of the reservoirs. According to the pore structure and clay mineral properties of low-permeability conglomerate reservoirs，this paper employed CT scanning，scanning electron microscopy，and X-ray diffraction to analyze the main factors causing potential damage in water injection from a multitude of perspectives. Additionally，according to the particle plugging theory，suspended solids（SS）in injection water will block the pore throat channel during the injection，resulting in a decrease in permeability and serious damage to low-permeability conglomerate cores. The experimental results show that there are large differences in the damage incurred by concentrations and median particle sizes of SS to the conglomerate cores. To achieve the goal of damage to the target reservoir less than 20%，SS concentration have to be ≤ 1.43 mg/L and median particle size ≤1.9 μm in the reservoir when the permeability is ≤ 9.28 mD；SS concentration ≤ 3.1 mg/L and median particle size ≤ 2.6μm in the reservoir when the permeability is in the range of 9.28-46.9 mD；SS concentration ≤ 5.1 mg/L and median particle size ≤ 4.8 μm in the reservoir when the permeability is ≥ 117 mD.