This invention relates to a casting control system of a die cast machine, and more particularly to a system for controlling a high speed injection real stroke of an injection plunger and controlling valve closing timing for degassing gas in a mold cavity. The high speed injection real stroke is measured by an arithmetic unit from a signal output from a position detector, and the high speed injection real stroke is then compared with a certain preset value. When arithmetic unit determines that the high speed injection real stroke and the preset value do not coincide with each other, a pretest action delay time of the injection plunger is .+-. incrementally or decrementally corrected until both values coincide. The arithmetic unit determines a start position of the high speed injection real stroke, outputs a signal to close a breathing valve at a position, to which is added or from which is subtracted a predetermined variable value with respect to the real start position and outputs a signal to open the breathing valve at a position where the injection plunger closes a molten metal feeding port.