The migration phenomenon of the melt flow front of multi-cavity micro injection molding process within the cavity is observed and analyzed using temperature measuring system equipped of integration of thermocouple sensor and visualization holographic tracer technique. The experimental results show that in the injection rate of 140-220 mm·s-1

the plastic melt front in the main runner is“U flow state”

while it is upper offset within secondary runner; in the injection rate of 10-70 mm·s-1

the plastic melt front in the main runner is“fountain” flow state

while it is down offset within secondary runner; and in the injection rate of 80-120 mm·s-1

the plastic melt fronts within both main and secondary runners have no obvious offset. The results indicate that the injection speed is different during the micro injection molding

leading to various shear heat and also melt front offset. Therefore

a nonequilibrium flow coefficient λ is introduced to determine the flow of the melt front and offset.