The invention belongs to a digitization measurement technology and relates to a measurement method of a long circular hole. A laser tracker, a target ball3 and a target ball seat 2 need to be used. A lower end epitaxial diameter of the target ball seat 2 should be consistent with a long circular hole perture. By using the method of the invention, a position deviation, an axial deviation and a deviation of a long circular direction of the long circular hole can be simply, rapidly and accurately measured and acquired.