Abstract: Accelerating the planning and construction of large-scale wind and solar energy bases in China's Gobi and desert areas is an important measure to achieve the "Carbon Peak" and "Carbon Neutrality" targets. Ultra-high Voltage Direct Current (UHVDC) power transmission of large-scale renewable energy power base presents strong stochasticity and volatility characteristics. The characteristics of cross-area power transmission have changed greatly compared with traditional UHVDC transmission. There is an urgent need to study UHVDC transmission curve planning methods suitable for uncertain environments. This paper considers the impact of uncertainties of wind power and photovoltaic (PV) output of renewable energy power base with UHVDC transmission. The operational characteristics of a renewable energy power base, UHVDC transmission, and regional network are modeled separately, and a stochastic planning method for UHVDC transmission based on scenario analysis is proposed. The results show that the transmission curve obtained by this paper can cover the transmission demand under different renewable energy output scenarios, verifying the proposed method's effectiveness.