This paper investigated some problems in steel tubuar joints design.The joint stiffness has played an important role in evaluating the whole stability of the structure. Currently there is no clear standard for judging joint stiffness, this paper presents a way to identify the steel joints stiffness. Accordingly, the analysis results of joint stiffness can be directly applied to practical engineering. This paper also proposed new steel welded joints which adapt to space slant and twisted surface for solving problem about square steel pipe joints design. This joints not only ensure regional stiffness and have an attractive appearance, simple structure, but also apply to engineering very well. The result of the research has a certain value to practical engineering design.