Abstract: Considering an inertial effect, a dynamic simulation for internal and external unbalanced shear flow phenomena on the geometrical equilibrium runner was performed by using the layered refining runner mesh technique, and the influence of technological factors on internal and external flow imbalance was investigated by an orthogonal experiment. The results indicated that flow rate presented a significant effect on the internal and external flow imbalance, and the internal and external imbalance index decreased with an increase of flow rate. The influence of melt temperature and injection pressure on the internal and external imbalance index was completely different, presenting an opposite trend.