Numerical studies were performed to design a linear slot virtual impactor with a cut-off size of 1 μm, operating at 150 LPM. A prototype model was designed with a general shape of a virtual impactor, numerical analysis was conducted, and the results were compared to a model with different design parameters. ANSYS FLUENT was used for numerical analysis, and an RSM model was used to calculate turbulence in the flow field. The particle trajectory was confirmed using DPM, and the collection efficiency and wall loss of particles inside the virtual impactor were calculated. The optimization was conducted by changing the angle and width of the acceleration nozzle. The CFD results show that reducing the angle of acceleration nozzle results in an increased cut-off size and decreased wall loss of large particles (> 4 μm).