A novel three-dimensional grain-based model based on Particle Flow Code is proposed. Within this model, both quantitative calculations and multi-level classifications of force chain networks are achieved. A batch of numerical samples with a single pre-existing fissure with different inclination angle αs is constructed and then applied to the uniaxial compression. The result shows that the general force chains (GF) are approximately uniformly distributed in each orientation. The number of high-strength force chains (HF) reaches its maximum at the peak load moment, and the main orientation is consistent with the loading direction. The average value of the force chain in the tip regions of the fissure at any characteristic moment is the highest. In the whole region and the upper and lower regions of the fissure, the level of the force chain network rises as αs increases. Conversely, within the tip regions of the fissure, both the average value and sum value of GF decrease. The fracture resistance of intragranular structures is the highest, surpassing that of both all structures and intergranular structures. The fracture resistance within the tip regions of the fissure is the lowest compared to the entire region and the upper and lower regions of the fissure.