Abstract: Due to the imperfections in calculation theory of a falsework design, it is difficult to ensure safety in its application, and consequently, occasional collapses of falsework arise. The paper makes a full-scale experimental study on falsework, obtains the limited bearing capacity and the instability mode, finds that when falsework is under the vertical load, the horizontal pole and scissors bar still bear a certain degree of internal forces owing to the imperfections of members and properties of nodes, and presents the concept of a generalized initial imperfection. In the numerical calculations, the study adopts the general finite element software ANSYS to set up a three-dimensional trussing calculation model on the basis of the experimental falsework, makes the generalized initial imperfection equivalent to the imaginary horizontal force and analyzes the nonlinear stability capacity. The experimental and analytical results show that the influences of the generalized initial imperfections on the structural stability should be taken into consideration in calculating falsework, and it is justifiable to set up the three-dimensional finite element model. The study lays a good foundation for the further research.