The invention discloses a self-adaptive compensation method for detecting the turning error of a large part of a rotary body, comprising the steps of: rough 
machining the part of the rotary body; measuring the 
radius of intersection of two adjacent 
contour line segments on an axial section of an inner hole of the part of the rotary body and en extent of error 
delta 1 of the 
radius of the two end points by a probe, performing semifinishing for the rough machined part of the rotary body, performing semifinishing for the semifinishing lathe tool by 
machining trajectory intersection and two end points with theoretical 
machining radius which is X1-
delta 1 / 2, measuring the actual radiuses of the intersection (A) and two end points (A1) in the step 2) after semifinishing to obtain an extent of error 
delta1' of semifinishing; performing finish machining, wherein that finish machining lathe tool, the main shaft rotary speed of the tool and the feeding speed are identical to those of semifinishing. In the process of finish machining, a 
numerical control system of the lathe compensates the extent of error delta 1' of semifinishing. The invention solves the problem that in the 
machining process the machining error caused by 
tool wear exists, thereby greatly improving the machining precision of the large part of the rotary body.