The invention discloses a precision casting method for an automobile turbocharger casing part. Firstly, a core of a scroll casing part investment pattern is made from dissoluble pattern wax; secondly, the core is placed in a metal forming press, and mould assembly and wax injection are performed to prepare the scroll casing part investment pattern; thirdly, mould opening is performed, the investment pattern is taken out, and the dissoluble core is dissolved; fourthly, the investment pattern is assembled and welded with a riser and a casting system to from a pattern assembly; fifthly, the pattern assembly is applied with coating material and sand; sixthly, an integral shell is manufactured through dewaxing and roasting; and finally, alloy liquid is poured into the shell, and a scroll casing cast is obtained through cooling solidification and unshelling treatment. The method not only effectively improves the dimensional precision of the scroll casing part and reduces surface roughness, but also greatly reduces and eliminates the defects of gas pore, slag inclusion, cold shut, shrinkage porosity and the like which are possibly caused by high cast gas evolution amount, low operating temperature and poor riser feeding effect.