The invention relates to a die-casting alloy material for a high-thermal-conductivity high-yield mobile phone middle plate and a preparation method thereof. The alloy comprises 10-12 wt% of Si, 1.0-2.0 wt% of Mg, less than 0.5 wt% of Mn, less than 0.5 wt% of Ce, less than 0.5 wt% of Zn, 0.1-0.5 wt% of Fe, 0.01-0.1 wt% of Ti, 0.005-0.1 wt% of Sr, 0.002-0.05 wt% of B, and the balance Al, wherein thecontent of other impurities is controlled below 0.01 wt%. Compared with the prior art, the Mn, Si, Mg and Ce are added into the aluminum alloy, a ternary strengthening phase Mg2Si, MnAl6 and Al11Ce3binary precipitation phase is introduced, the yield strength and the elongation rate of the material are remarkably improved, meanwhile, the Ce and B elements are doped into the aluminum alloy, and the thermal conductivity of the die-casting alloy is greatly improved by utilizing the performances of the Ce and B elements.