Abstract: To address the frequency stability issues caused by high-penetration photovoltaic (PV) integration and to reduce PV curtailment losses, this paper proposes a bi-level optimization method for dynamic deloading ratio calculation that balances the cost-effectiveness and frequency regulation performance of PV participating in primary frequency regulation (PFR). In the upper level, an optimization model is established to minimize the comprehensive cost of PV-based PFR, where the cost function incorporates economic indicators including PV rated power, deloading ratio, and left and right droop coefficients, along with a frequency deviation penalty model over the operational cycle. This optimization problem is solved using the CPLEX solver in MATLAB. In the lower level, a refined management strategy for PV reserve capacity is proposed, whose control logic is based on the deloading-droop control characteristics of synchronous generators. The optimization objective of this level is to minimize the root mean square (RMS) value of frequency deviation, and an improved particle swarm optimization (IPSO) algorithm is employed to obtain the optimized frequency deviation sequence and the optimal dynamic deloading ratio curve. Finally, the proposed method is compared with multiple fixed deloading ratio strategies and an existing variable deloading ratio strategy through simulations. The results demonstrate that the proposed method achieves a dual optimization of technical and economic objectives, significantly reducing economic losses while maintaining satisfactory frequency regulation performance.