A disposable safety injection apparatus includes a liquid medication tube, a syringe needle, a push rod, and a tube ring. The syringe needle is connected to an insert tenon at a front end of the liquid medication tube. The insert tenon includes a connecting portion having concentric C-shape lacerable slot and circular lacerable slot respectively disposed at a connecting position of a top wall at the front end of the liquid medication tube and the connecting position of the top wall and an external side of the tube ring. A rod column having a latch portion is extended axially from the front end of the body of the push rod, passed through and fixed to the tube ring, such that the rod column can be slidably contained in liquid medication tube. The push rod is pushed forward to press the tube ring against top wall and latch the latch portion to a connecting portion in the insert tenon. The push rod is pushed further to lacerate the C-shape lacerable slot and form a torque onto a position having no groove, and thus the circular lacerable slot breaks at a thinner position and lacerates along the periphery. By then, the push rod is pulled backward to separate the liquid medication tube after the force is applied onto the circular lacerable slot.
