Planting trees around buildings has traditionally been a widely adopted landscaping strategy for enhancing aesthetics. Nevertheless, the potential influence of these trees on the natural ventilation within buildings has often been neglected and remains insufficiently explored. To improve the performance of indoor natural ventilation and air quality in buildings, this study introduces a new Computational Fluid Dynamics (CFD) fast simulation method tailored for architectural and landscape design scenarios involving trees planted around the building. Numerous factors such as building layout and dimensions, window and door placements, trees arrangement, tree canopy dimensions, vegetation leaf area density, drag coefficient, wind direction, and wind speed are taken into consideration. The parametric modeling, simulation, and post-processing processes are developed using a combination of Python and CFD software. This integrated approach could assist architects in optimizing their designs, with a specific emphasis on achieving precise indoor ventilation efficiency during the initial design phase of a building. Finally, the parametric CFD batch simulation method is employed to explore the impact of changes in tree positions on indoor ventilation to validate the practical applicability of the approach. In the given case study, the dimensions and placements of the building, doors, and windows remain constant, while alterations in the positioning of trees result in varying indoor wind environment performances influenced by different wind directions. The parametric batch CFD processing method improves the simulation speed, and also enables the selection of recommended and optimal cases for tree locations under different wind directions from 200 different cases.