Abstract: To address the difficulty in predicting residual stress during laser melting deposition of Ti6Al4V titanium alloy, a coupled thermo-metallurgical-mechanical modeling study was carried out. Building upon an existing solid-state phase transformation model, a thermo-metallurgical elasto-plastic constitutive model was developed by introducing transformation-induced volumetric strain and the evolution of mechanical properties in mixed phases. Subsequently, a numerical simulation model capable of reflecting thermo-metallurgical-mechanical interactions was established. Experimental verification demonstrated that the coupled model significantly improves the prediction accuracy of residual stresses. Compared with the conventional thermo-mechanical coupled model, the average prediction error was reduced by approximately 65.7%. Strain history analysis further confirmed that the improvement mainly originated from the consideration of volumetric strain induced by solid-state phase transformation during cooling. Based on the model, the effects of laser power, scanning speed, interlayer dwell time, and number of deposited layers on residual stress were systematically analyzed, providing a theoretical basis for process parameter optimization.