Shear lag effect in structural engineering is a prevalent mechanical phenomenon, as small as a component, as large as a super high-rise building, there will be shear lag phenomenon.Shear lag, sometimes called shear lag, from the nature of mechanics, is the principle of St. Venant, the specific performance is in a local range, the role of shear force can play a limited role, so the distribution of positive stress is not uniform, the phenomenon of uneven distribution of positive stress is called shear lag.Walls on the formation of a hole in the hollow body, also known as the box tube, after the opening, due to the deformation of the beam so that there is a lag phenomenon of shear transfer, so that the positive stress distribution in the column is parabolic, known as the shear lag phenomenon.