Abstract: The laser cutting machine needs to be re-calibrated for processing accuracy when it is used for some time, which greatly reduces the use efficiency and economical efficiency. To solve this problem, the influence of the creep behavior of the beam for machining accuracy is analyzed. Firstly, based on the Wumansky theory about constrained torsion of thin-walled beam, a simplified model for theory calculating the creep of beam guideway-slider-laser emission hole is established. Secondly, the finite element software is used to simulate the creep behavior of the beam, and the creep mechanism of the laser emission hole in the x and z directions is studied by combining the theoretical calculation data. Then, it is found that the x-direction creep of the laser emission hole plays a leading role in processing stability, and the thickness and section shape of the beam are the main parameters related to its performance. Finally, by optimizing the cross section parameters \delta \left(s\right) and \rho \left(s\right) of the beam and increasing the \varOmega ^2/J_d values, the creep resistance of the beam is improved. The above research is helpful to improve the processing stability of laser cutting machine in long-term operation, and has good engineering application value.