Abstract: Particle Arc Therapy (PAT) represents a cutting-edge innovation in modern radiation therapy, encompassing two principal modalities: Spot-Scanning Proton Arc Therapy (SPArc) and Spot-Scanning Heavy Ion Arc Therapy (SHArc). By delivering beams continuously along an arc trajectory, PAT enables highly conformal dose distributions and improved sparing of organs at risk (OARs), particularly in complex anatomical sites. Existing studies have demonstrated that, compared with conventional Intensity-Modulated Proton Therapy (IMPT), SPArc can reduce the mean OAR dose by approximately 10–20% (p < 0.05), while achieving enhanced plan robustness and delivery efficiency. SHArc, benefiting from the high Linear Energy Transfer (LET) characteristics of heavy ions, is theoretically advantageous for the treatment of radioresistant tumors. This review provides a comprehensive overview of the physical and technical foundations of PAT, its planning optimization strategies, and recent clinical and preclinical developments. Challenges related to robustness verification, motion management, and cost-effectiveness are also discussed. Overall, PAT—particularly SPArc—exhibits promising translational potential and is poised to become an important direction in the future of precision radiotherapy.