The visual quality of a fabric is directly connected with the fabric density, i.e., picks/em and ends/em, variations of which are influenced by the weaving process conditions. Any variation in the conditions during a weaving process can lead to a fabric flaw, which implies a deterioration of the fabric quality. The fault that appears frequently in weaving is the stop mark, the variation in fabric density, especially, weft picks per unit length. This research is to set up a model describing the pickspacing dynamics in the weaving process and to simulate the pickspacing changes under given initial conditions, considering the start-up velocity profiles. The results show that initial clothfell position is an important factor affecting the pickspacing unevenness. Thin and harsh-surfaced weft yarns are more sensitive to the pickspacing changes than the thick and even-surfaced, while a velocity profile for a restart, even not considering the dynamics of the machine parts, can bring about a stop mark, if the profile has a quadratic function form with respect to time.