Abstract: Existing ultra-precision surface roughness prediction models fail to account for the effect of tool wear conditions on surface formation, resulting in low accuracy in machining quality prediction for difficult-to-cut materials. To solve this problem, a surface roughness model for ultra-precision orthogonal cutting is developed based on a BP neural network and physical feature driving. This model integrates the impacts of rake face and flank face wear during diamond cutting of Ti-6Al-4V titanium alloy (hereinafter referred to as TC4).First, a three-dimensional finite element (FE) simulation model is built to simulate the wear morphology of the rake and flank faces of the diamond tool in orthogonal cutting of TC4 alloy. Model validity is subsequently verified via experimental tests. On the basis of the existing surface topography generation model for diamond orthogonal cutting, the elastic recovery and plastic side flow effects of TC4 are incorporated, and the rake face contour extracted from finite element simulation is imported to construct a surface generation simulation model for diamond orthogonal cutting. Using this model, the geometric base roughness (Ra_geo) determined by variations in the rake face profile is calculated.Furthermore, to overcome the limitation that analytical models cannot characterize the influence of flank wear land on surface generation, a physical-feature-driven BP neural network prediction model for surface roughness is proposed. The input variables include cutting depth (a_p), cutting length (L), as well as physical feature parameters obtained from FE simulation and analytical modeling (flank wear width VB and geometric base roughness Ra_geo), and the output is the experimentally measured total surface roughness (Ra_total). Multiple groups of experimental datasets are used for network training, ultimately finalizing the physical-feature-driven surface roughness prediction model. Experimental results demonstrate that the developed model exhibits favorable prediction accuracy under various machining parameters for diamond cutting of TC4 alloy.