Abstract: Through the test and finite element simulation analysis of the flexural stiffness of bottom box of removable box house, the load-displacement curves of the bottom frame beam at the 1/4 section, the middle span and the bottom frame center were compared. The results showed that the finite element simulation results were in good agreement with the experimental results, and the reliability of the finite element analysis was verified. Based on the finite element numerical simulation, the influence of the four factors on the flexural stiffness of bottom frame, such as calcium silicate board floor, corner opening, column and top and bottom frame bolted connection stiffness, corner piece corner constraint was analyzed, and the mid-span versus displacement curves of the bottom frame beam under different influencing tactors were obtained. The resulets showed that the connection between the column and the top and bottom frame was a semi-rigid connection. The influence of the opening of the corner piece on the mid-span load versus displacement curve was small, the connection stiffness of the calcium silicate board and the bolt, and the bending stiffness of the corner had a greater impact on the flexural stiffness, so these factors should be considered in the analysis.