The nib of marker pen is one of the most important sections which has a fibrous porous structure. The interfiber space in a nib is a capillary occupied by liquid ink. When the porous fibrous structure is in contact with a liquid, its capillaries wetted by the liquid. As the wicking phenomenon is widely used in textile industry, the control of capillary penetration kinetics in the textile processes is needed. Also, the motion and speed control of liquid in the fibrous nib is very important and have a significant impact on its quality. The effective parameters on the wicking coefficient of liquid in the fibrous nibs include fiber type, fiber fineness, the interfiber space, porosity and the resin which is used to stabilize the construction. The aim of this study is the evaluation of effective structure parameters on the performance of marker nib. The polyester fiber tows with certain count and different fineness putted into the frame and then heat setted at the different temperature and time. Afterwords samples were coated with three different resins. The wicking horizontal test was done before and after coating process. Also, the initial diameter of heat setted tows and their final diameter after 24 hours were measured and variations in diameter deformation were calculated. The curves of liquid distance advanced vs the square root of time follow the Lucas Washburn in all samples. The results showed that the setting conditions (temperature and heating time), tow count and fiber fineness have significant effect on the horizontal wicking coefficient of ink in the obtained nibs. Increasing the setting temperature from 180? C to 220? C and setting time from 30 to 60 minutes reduced the variations in diameter from 30.58% to 5.37% which resulted in the increase in horizontal wicking coefficient from 2.23 to 2.77 mm/s 0.5 . Also increasing the tow count from 5.5 to 6.5 g/m, due to increase in the number of fibers in the frame cross section, sever heat setted was obtained. Variations in diameter reduced from 59.96% to 5.82% leading to increase of coefficient horizontal wicking from 2.23 to 2.56 mm/s 0.5 . When the fiber fineness increased from 3.6 to 2.4 dtex, coefficient horizontal wicking was increased and the diameter deformation was reduced. Key words: Wicking Phenomenon, Wetting, Marker Pen, Felt Nib, Heat Sett