The invention relates to a method for detecting shape change of a metro tunnel section. The method comprises the following steps: with a center line of a tunnel track as an original point, establishing a rectangular coordinate system of the metro tunnel section; according to an angle meter, a laser ranger and a laser scanner, performing data measurement on the tunnel section to obtain a coordinate offset angle alpha and coordinates of all measuring points of the metro tunnel section in the rectangular coordinate system, wherein the coordinates of an ith measuring point is (xi, yi); by an elliptic fitting algorithm, performing curve fitting on basic measurement data to obtain a shape parameter, meeting an error requirement, of the tunnel section; judging whether the offset between the shape parameter of the tunnel section and a historical shape parameter exceeds an offset threshold, if yes, indicating that the metro tunnel section has obvious shape change, otherwise, indicating that the metro tunnel section does not have obvious shape change. Compared with the prior art, the method has the advantages of high measurement accuracy, comprehensive measurement, convenience in implementation and the like.