This study aims to explore the exception to the Roche limit theory: the planetary ring of Quaoar. Stable planetary rings typically form within the Roche limit; however, the rings of Quaoar are stably located outside the Roche limit. Therefore, our research objective is to explain why the Quaoar ring can exist outside the Roche limit. We focus on investigating factors such as density, rigid body and fluid properties, the principles of orbital resonance, and comparing other ring systems. Ultimately, we will use force analysis and compare similar ring systems to infer the reasons for the stability of the planetary ring. Based on our research, we believe that the Quaoar ring is influenced by the gravitational effect of its moon Weywot, with orbital resonance increasing the distance between ring particles, preventing them from coalescing into a moon outside the Roche limit. Through an in-depth study of the factors affecting the Roche limit and the formation of planetary rings, we hope to reveal the physical mechanisms behind the formation and stability of the Quaoar ring, thereby expanding our understanding of planetary ring formation and celestial mechanics. Additionally, we hope this research can provide a reference for future studies on other similar exceptional cases of planetary rings