The invention discloses a method for measuring a pull-press and bending composite deformation field of a variable cross section beam structure. In this method, a pure bending strain of a bent surface of a to-be-measured structure is the different between a composite strain, caused by the pulling or pressing of a bent surface a in an x direction and the bending deformation in a w direction, and the pulling or pressing deformation of a neutral layer of the structure on a side surface b. The method comprises the steps: firstly solving the pure bending deformation of the surface a of the structure at the position of a strain sensor and the pulling or pressing strain of the side surface a according to strain values, measured by the strain sensor, of the surface a and the side surface b; secondly respectively solving the pulling or pressing deformation and bending information of the two surfaces at the position of the strain sensor according to the theories of mathematic integration and displacement; and finally solving the composite deformation field of the structure through employing the two types of deformation. The method effectively solves problems in the prior art that a reference is difficult to set, the reference is liable to deform, and a measurement is limited.