The invention relates to a demarcation detection method for a residual stress experiment. The demarcation detection method is characterized by comprising the following steps: (S1) pasting a piece to asite which is r from the center of a hole, and fetching a test piece with a width being greater than a radius a of a small hole drilled in a measured point by 4-5 times; (S2) loading the undrilled test piece step-by-step on a material testing machine, calculating a strain sigma of the test piece, and measuring strains epsilon'1 and epsilon'2 under various levels of loads, (S3) taking down the test piece, drilling a hole in an appointed part of the test piece, re-stretching the test piece, and measuring strain values epsilon''1 and epsilon''2 after the test piece is drilled; and (S4) calculating residual stresses sigma1 and sigma2 and a numerical value of an included angle phi. The demarcation detection method is high in measurement accuracy, good in linearity, small in temperature excursion and applicable to long-term reliable working and can be widely applied to comprehensive tests of physical quantities of strains, stresses, displacement, pressure and the like in industrial fields,research, development and testing centers of enterprises, and teaching experiments of universities.