According to its characteristics,a die casting die for aluminum alloy magnifier frame was designed.Structure characteristics and working principle of the die were described.Some design was adopted in the die,such as one mould-two cavities and side-gating system with rectangular cross section for feeding,contracting core for core pulling and rotating core for thread demoulding.Core that forms loop groove of hole-wall of the castings is designed of 6 large sector segments and 6 small sector segment,which realizes the core-pulling of loop groove by relative motion of large and small sector segment making 12 sector segment move inside along radial direction.Meanwhile,with the help of open-mould force to transmit gear-rack mechanism,thread demoulding can be realized by rotating horizontal thread core.The die exhibits advantages of compact structure,reliable working performance,high efficiency and high product precision.