A mold was developed for injection-compression molding experiments. The cavity was designed to be closed to prevent melt leakage in the situation of partial mold opening for injection. In order to investigate the effects of melt backflow on cavity pressure during mold compression, one valve-gate hot runner system was built into the plate mold. From experiments under different compression strokes, it was noted that relatively much more melt backflow took place near the gate, during mold closing with increased compression stroke. The effects of compression stroke and compression speed on the cavity pressure were investigated by injection-compression molding experiments. In the case of large compression stroke, the pressure during switching to mold compression significantly dropped near the gate. The cavity pressure decreased in magnitude, and became more uniform over the entire cavity with decreasing compression speed. In addition, the larger compression stroke resulted in increasing the part thickness, but the effect of compression speed on thickness was very small.