Tempered martensite can be formed at surface of bar to increase its mechanical properties by higher efficient tube type turbulent flow cooling system after hot rolling of bar products. The temperature field of Φ25 mm Q215 steel bar after hot rolling in turbulent flow process has been analyzed by the finite element analysis software MSC. Marc. Results showed that left turbulent flow system cooling for 1 s the surface temperature of bar decreased from 950.0℃ (finishing rolling temperature) to 768. 0 ℃ and the centre temperature of bar decreased to 861. 2 ℃ ； and as bar was out of turbulent flow cooling system for 3 s the surface temperature increased to 792. 6 ℃. Production application results indicated that the ultimate strength of hot rolled bar cooling by 3 zone turbulent flow cooling was up to 410 MPa while that by normal process cooling was only 310 MPa.