The invention discloses a deep-hole and thin-wall cylinder barrel machining method, and relates to the field of machining, in particular to the deep-hole and thin-wall cylinder barrel machining method. The deep-hole and thin-wall cylinder barrel machining method comprises the following steps: blanking: a seamless steel pipe is selected; and a certain machining allowance is retained; rough turning:a workpiece is clamped on a lathe; and an inner hole and an outer circle of the workpiece are roughly turned; semi-finish turning: the semi-finish turning is performed on the inner hole of the workpiece; and a redundant part in the length direction of the workpiece is turned off; and finish turning: a positioning guide sleeve is mounted in a main shaft inner hole of the lathe; an external coolinglubricating liquid pipe is inserted from the back end of the main shaft hole to connect with an inner hole finishing cutter; a guide sleeve part of the inner hole finishing cutter is installed in theinner hole of the positioning guide sleeve beforehand; the length of a cutter body of the inner hole finishing cutter is determined according to the length of the workpiece; and a connected part of acutter tail can be guaranteed to expose from the inner hole of the machined workpiece. The deep-hole and thin-wall cylinder barrel machining method can improve the production efficiency, guarantees the workpiece machining quality, reduces the production cost, and reduces the worker labor intensity.