The paper discusses CAD design on the pores created with simple units such as cylinder, whose structures are determined by unit space array mode and size. Pore ratio, independent to unit models, only relates to orifice diameter and scanning space in fused deposition manufacturing (FDM). Mechanical strength is measured to verify the influences of array modes and inside sizes. The tests demonstrate that 0/90°array mode has larger strength and that the cylinder bears the more pressure along the axis. Stress-strain curve reveals the 4 sections when the parts deform, including linear stage, slightly change stage, increasing stage and damage stage.