Laser-based Powder Bed Fusion （L-PBF） is an additive manufacturing technology using a high-energy-density laser beam to completely melt the metal powders on the powder bed layer-by-layer until the part is obtained. The spatters，caused by the laser beam，can reduce the part quality when they are deposited on the workbench. Using a negative pressure pipe moving with the scanning laser to control the spatters is a feasible approach to reduce the particles deposited on the workbench. In this chapter，a Computational Fluid Dynamics （CFD） model for the flow field in the L-PBF printer was developed and coupled with a discrete phase model （DPM） simulating the trajectory of spatters ejected from the workbench. A negative pressure pipe was proposed to move with the scanning laser and absorb the ejected spatters. The impacts of the diameter，outlet flow rate of the negative pressure pipe，and initial velocity of spatters were investigated numerically. The results show that the percentage of spatters deposited on the workbench decreases from 70.5% to 40.6% after using the pipe. When the outlet flow rate is 500 L/min，the deposition rates at the pipe diameter of 40 mm，50 mm and 60 mm are 33.05%，40.64% and 40.05%，respectively. When the pipe diameter is 50 mm，the deposition rates at an outlet flow rate of 500 L/min，600 L/min and 700 L/min are 40.64%，30.72% and 23.61%，respectively. The results verify that using the negative pressure pipe is a feasible approach to efficiently reduce the spatters deposited on the workbench. 288gOKgU2YTxO0x1vL0uGXGl63fgT4xzGQ/5TJD3YKyUI46ssKhv+XlOEX3ayvj7