Abstract: Temperature field of hot rolled strip was calculated according to the partial differential equation of heat conduction and the boundary and initial condition， and the lumped parameter analysis method which neglects temperature gradient along the thickness. The equations of relative deviation for the two temperature calculation models， assuming the former was accurate， were obtained， and the equations were calculated by Matlab. The application range of temperature calculation model obtained by lumped parameter analysis method were obtained. The ranges of Biot were 0～0.1008， 0～0.1361 and 0～0.9593 for the central， 1/4 and surface of strip， respectively， when the relative deviation was less than 5%， and the ranges of Biot were 0～0.2033， 0～0.2782 and 0～1.4974 for the central， 1/4 and surface of strip， respectively， when the relative deviation was less than 10%.

Key words: hot rolled strip, lumped parameter analysis method, temperature calculation model, relative deviation, Biot