Stability is the key and difficult point in steel structure teaching. As a supplement of he basic principle of steel structures course in civil engineering, Tongji University took the lead in building a multi-functional teaching experiment platform for steel structures in China, which combines theoretical teaching with laboratory practice. Experiment for overall stability of steel beam is one of the most ornamental experiment. However, teaching experimental results in the past few years showed that overall stability bearing capacity were higher than theoretical values because of support of beam, which had a negative effect to teaching. In order to simulate boundary conditions of steel beam accurately, the author improved the support, making the experimental values closer to the theoretical values and thus achieving good teaching effect.