This study predicts and analyzes thermal history in relation to microstructure in laser-directed energy deposition (L-DED) process with wire feedstock made of UNS S32205 duplex stainless steel (DSS). This dual-phase alloy with an austenitic-ferritic microstructure offers excellent properties like mechanical strength and corrosion resistance making it ideal for applications such as marine engineering and chemical processing. L-DED with wire feedstock is an additive manufacturing (AM) process through layer-by-layer deposition standing out for large-scale production due to its fairly high deposition rate (8 kg/h). However, experiments show that high-rate processing often leads to metallurgical defects such as unmelted wire residues, porosity, and cracks. These issues arise from non-linear molten pool dynamics, interlayer thermal cycling, and solid-state phase transformations, which traditional observation methods struggle to analyze. To address this, a 3D transient heat transfer model was developed in COMSOL Multiphysics. This model was applied to analyze cooling rates and temperature gradient changes during multi-bead and multilayer deposition.Through simulation software, the deposition process of additive manufacturing technology was successfully modelled. Additionally, the internal temperature variation curves of the deposition layer were obtained via the simulation, enabling the prediction of microstructural constituents. These predicted constituents were consistent with those observed in the actual deposition layer, fully validating the reliability of the simulation model. By employing simulation-based modelling to predict and analyze the microstructure within the deposition layer, the quality of the manufactured components can be effectively enhanced.