Abstract: By the end of 2025, the installed photovoltaic capacity in Zhejiang Province reaches 64.29 GW, making photovoltaic power the largest power source in the province. With the high penetration of grid-connected photovoltaic power, photovoltaic output is often mismatched with load demand during holiday low-load periods, when industrial and commercial electricity consumption decreases. This mismatch may cause reverse power flow and voltage limit violations, leading to prominent photovoltaic accommodation challenges. This paper proposes a market-oriented trading optimization strategy for foundry industry loads participating in virtual power plant valley-filling. It explores the valley-filling potential of the traditional foundry industry and constructs an electricity cost model for production scheduling optimization considering peak-valley price differences and valley-filling subsidies. By guiding foundry enterprises to implement off-peak production, the proposed strategy reduces enterprise electricity costs and improves photovoltaic accommodation efficiency. The feasibility of county-level small foundry clusters participating in valley-filling is verified, and the proposed model shows potential for wider application.