The microstructure， second phase， fracture morphology， mechanical properties of high-strength rebars were characterized by metallographic microscope（MM）， scanning electron microscope （SEM）， transmission electron microscopy（TEM） and universal tensile testing machine. The results show that the microstructure of 1^#-3^# experimental steel rebars are ferrite + pearlite， and the 3^# experimental steel rebar contains a small amount of bainite；the main precipitate of 3^# rebar experimental steel is niobium vanadium composite carbonitride （（Nb，V） （C，N））， which is round in shape and precipitate on ferrite grain boundary and pearlite lamellar， with the average particle size of 10 nm；the tensile fracture of 1^#-3^# experimental steel rebars belong to ductile fracture， and the equiaxed dimples are distributed on the fracture；with the increase of Nb content， the tensile strength and yield strength of experimental steel rebar increase，the elongation after fracture decrease；the tensile strength and yield strength of 3^# experimental steel rebar is the largest，reach 795，525 MPa，respectively，the elongation after fracture is 21.6%.