The effects of Cu

Mg

Mn elements on tensile strength of Al-24Si piston alloy at high temperature have been examined based on orthogonal regression design

and the parabola equation between tensilestrength at 300℃ and three elements have been established.The results indicate that the change of tensile strength of Al-24Si piston alloy with P

MM（mistch-metal） and Sr compound modification can be neglected with changing Cu and Mg elements in a given range.The Mn content

such as in range of 0.2% to 0.31% or of 0.51 % to 0.6 %

can be emphatically determined and the calculated minimum tensile strength of Al-24Si alloy at 300 ℃ is about 127.39 MPa by the fitting e-quation.which can ensure tensile strength at 300 ℃ to meet the service requirements.