Abstract: Large-scale renewable energy power base with UHVDC will play an important role in China. Optimizing the medium and long term operation modes of UHVDC can help to promote the accommodation ability of renewable energy base. This paper proposes a time sequential production simulation based method on optimization of medium and long term operation modes of UHVDC. Firstly, to balance the computational complexity and precision, aggregated operation models of different types of concentrating solar power (CSP), thermal power unit and battery energy storage system (BESS) are established. Secondly, with considering the operation modes, flexible operations and peak-load regulation demand of receiving-end power grid, an UHVDC operation model without integer variables is established. Thirdly, a mathematical model is formulated to optimize the weekly operation modes of UHVDC, which the objective is to maximize the annual power generation of renewable energy, and a sequential algorithm is proposed to solve the annual optimization model week by week. Finally, case studies are conducted by a renewable energy power base with wind power, photovoltaic power (PV), CSP, thermal power and BESS. Testing results verify that the proposed method can optimize the operation modes of UHVDC and maximize the power generation of renewable energy through UHVDC. The computational precision and efficiency also satisfy the applicability in practice.