Abstract: The mechanical properties of hot rolled ribbed steel bars change with time, which makes the mechanical properties tested by manufacturer different from those tested by consumers. In order to find out the change characteristics of mechanical properties of hot rolled ribbed steel bars in different time periods, the mechanical properties of hot rolled ribbed steel bars in different time periods were tested. The results show that the mechanical properties of hot rolled ribbed steel bars changed rapidly within 10 d (days), and tend to be stable after 20 d. The change rule is that the yield strength decreased, the tensile strength, the elongation after breaking and the total elongation under maximum force increased. The yield strength decreased by 17.31 MPa at most. It is suggested that the yield strength should be 20 MPa higher than GB when enterprises formulate internal control standard.