Abstract: In the low-altitude economy scenario, the uplink communication of an unmanned aerial vehicle（UAV）may face a complex and easily obstructed channel environment. A reconfigurable intelligent surface（RIS）is employed to introduce a reflection path for data transmission, and single-carrier frequency-domain equalization（SC-FDE）is adopted at the receiver to improve the anti-multipath capability. The system performance is then optimized by adjusting the reflection coefficients of RIS elements. However, existing literature usually assumes perfect channel state information（CSI）is available, without considering estimation errors. In this paper, we propose a RIS optimization algorithm based on the channel estimation results. The reflection coefficients are optimized using an iterative algorithm to maximize the received signal-to-noise ratio. Simulation results indicate that the optimized system can achieve about 5 dB gain at a bit error rate of 10⁻³ compared to the unoptimized one, which demonstrates the effectiveness of the proposed algorithm.