The injection die has a mold plate that has a main arm, a compressed board serve to lock down the mold insert within the mold plate and an ejection mechanism. The ejection mechanism has a columned ejector pin with a stopping protruded from one end of the ejector pin, an elastic module installed in the main arm to abut against the ejector pin to provide an elastic force, and a fixed board received in the main arm to withstand one end of the elastic module.