Abstract: Based on the properties and stress characteristics of space frame structures under fire,the nonlinear finite element numerical simulations are performed on the properties of the welded hollow spherical joints bearing axial compression under fire with the thermal parameters specified in the EUROCODE 3 and the standard fire temperature-time curve ISO834.The distribution law and influencing factors of the temperature fields are analyzed.By analyzing the stress and displacement variation characteristics of the welded hollow spherical joints under fire, their failure modes are determined．The results show that decreasing the load ratio or increasing the thickness of the welded steel pipe can prolong the ultimate fire- resistant duration, and the steel tube root is the weakness of the welded hollow spherical joint bearing compression under fire．