The invention relates to an aluminum 
alloy for a special high-pressure 
oil pump shell and a preparation method thereof. The 
alloy comprises the ingredients by weight percent: 5-7% of Si, 1.3-1.7% of Cu, 0.4-0.7% of Mg, 0.1-0.35% of Mn, 0.2-0.3% of Ti, 0.4% or less of Fe, 0.01% or less of Sn, 0.01% or less of Pb, 0.03% or less of Ca, 0.05% or less of single 
impurity, and the balance of aluminum, wherein the total impurities are 0.15% or less. The preparation method comprises the following steps of: 
smelting at 755-765 DEG C; spraying a common refining agent by 
argon at 745-755 DEG C; evenly scattering a 
sodium modifier under the temperature which is 740 DEG C at least, standing for 10-20 minutes; 
casting by a semi-continuous direct 
water cooling method; homogenizing a cast 
ingot, naturally cooling after discharging from a furnace; and carrying out heat treatment 
quenching after extruding and molding the homogenized cast 
ingot, and finally carrying out 
precipitation heat treatment. The aluminum 
alloy has the beneficial effects of good high temperature performance, thermal deformability, 
abrasive resistance, gas tightness and the like, is good in 
casting and extruding properties, and can be well applied to the special high-pressure 
oil pump shell.