The invention relates to a machining method of a low-pressure compressor casing. The method comprises the following steps that 1, a blank is inspected; 2, a benchmark is turned; 3, spinning is carriedout, wherein the blank is subjected to drawing and spinning by using a powerful numerical control spinning machine, so that a workpiece is obtained, wherein the wall thickness delta and the roundnessof the workpiece are controlled to be within 0.1 mm, and a small amount of allowance is reserved at the two ends of the workpiece to be used for subsequent mechanical machining; 4, the workpiece is cleaned, wherein a lubricant on the surface of the workpiece is cleared; 5, heat treatment is carried out, wherein the spinning stress is eliminated through the heat treatment; 6, a finish turning is carried out on a front end of the workpiece and a rear end of the workpiece; 7, the end face holes at the two ends of the workpiece is drilled and bored; 8, stamping of blade-type grooves is carried out, wherein a numerical-control punching machine is used for equidistantly stamping the blade-shaped grooves on the workpiece in the radial direction and fine trimming is carried out, so that the position degree of the blade-shaped groove is ensured to be 0.2 mm, and the contour degree of the blade-shaped groove is 0.05 mm; 9, magnetic particle testing is carried out; and 10, checking and storing are carried out. According to the method, the requirements of case deformation control, surface quality control and cost control can be met.