In order to improve the performance of thin-walled engine casing with geometrical errors,a limit detection method was studied. The deformation law of constrained surfaces and related surfaces was studied by changing the constraining mode of constrained surfaces. Different constraining modes can limit constrained surfaces, with a limit of 0.064 mm and a limit of 0.052 mm on relevant surfaces. When there was only a single constraint factor, the change of pressing plate position had a greater limiting effect on the constrained surfaces than the number of pressing plates and the pressing force. Considering the three factors comprehensively, when the pressing force was large, the number of pressing plates was large and the deformation of pressing plates was large, the limiting effect of constrained surfaces was better. The results show that the relative error between the predicted value of simulated assembly and the measured value is within 10%. The finite element model is accurate and effective, which can predict the assembly of casing parts, improve the assembly quality of casing parts, and provide feedback information for the manufacturing end.