Selective laser melting (SLM), the main additive manufacturing process, has been extensively used in manufacturing. The scanning strategy is one of the key parameters that affects the forming performance. In this study, two of the most popular scanning pathways were selected as the research objects to show their effect on thermodynamic laws. First, a thermodynamic coupling simulation model conforming to the characteristics of the SLM process was established, and a secondary development was performed based on finite element software to realize the simulation development of different paths. Then, a set of process parameters was used as a simulation example. The results show that the weld pool geometry and thermal stress of the striped scanning path are bigger than those of the chessboard pattern. Finally, several experimental datasets, including molten pool morphology and residual stress tests, confirmed that the simulation results were accurate. This study shows how the scanning trajectory affected the thermodynamics of SLM forming and provided an effective process simulation technique for engineering practice, which is convenient for SLM forming quality prediction analysis.