Abstract:Based on the problems of the modification of stiffness matrix and the positioning of added structures in the step by step modelling method, a method which divides each construction stage into beginning phase and end phase and analyzes different phases respectively was proposed. Subsequently, a new method for modifying the stiffness matrix of structures was developed in construction process analysis of steel structures. Meanwhile, to determine the position of the added structures, a correction positioning method of design configuration was advised herein. Consequently, the existing step by step modelling method was improved. Furthermore, to simulate the construction process of a twostory frame, the improved step by step modelling method was programmed in Matlab software. The numerical results of the improved step by step modelling method were compared with those of state variable superposition method, birthdeath element method and one step forming method. It is shown that the modification methods of stiffness matrix and the positioning of design configuration are reasonable, effective and accurate.