Abstract: The effects of Ti and Zr content on the microstructure and mechanical properties of centrifugal casting 25Cr35NiNb steel furnace tube were studied by means of direct reading spectrometer, field emission scanning electron microscope and high temperature lasting testing machine. The results show that the micro addition of Ti and Zr improves the carbide precipitation at grain boundary of the furnace tube steel, and significantly affects its high temperature rupture property.(Nb, Zr)C and ZrC precipitates are found in the original as cast austenite structure of the furnace tube with 0.136wt%Zr element.After high temperature lasting test, the niobium bearing phase is mainly NbC without G phase transformation; the original as cast austenite structure of 25Cr35NiNb furnace tube with 0.111wt%Ti and 0.10wt%Zr element contains TiC, (Nb, Ti)C and ZrO precipitates, after high temperature lasting test, the niobium bearing phase in TiC and ZrO precipitates is mainly(Nb, Ti)C, without G phase transformation.The formation of Ti and Zr carbides retards the transformation of NbC to G phase in 25Cr35NiNb alloy f urnace tube at high temperature. When the Ti+Zr content is 0.06wt%-0.18wt%, the centrifugal casting 25Cr35NiNb furnace tube has a long high temperature rupture time under the test temperature of 1100 ℃and the test stress of 17MPa.