Curved aluminium alloy thin-walled workpieces are an integral part of essential components in aerospace. Aggressive machining parameters can reduce the machined surface roughness and dimensional accuracy during flank milling for the thin-walled workpiece. However, conservative machining parameters can constrain the machining efficiency. To solve this issue, this article develops a machining parameter optimization method for curved thin-walled workpieces during flank milling. The method comprehensively considers the impact of time-varying deflection and material removal of curved thin-walled workpieces during the flank milling and further analyses the influence of machining parameters on machining surface roughness and dimensional accuracy. The optimized processing parameters can maximize the processing efficiency for curved thin-walled workpiece to satisfy the processing dimensional precision and surface roughness.