To understand the high temperature flow behaviour of a novel pearlitic steel (PS) and low carbon steel (LCS) bimetal, hot compression tests in a wide range of temperature and strain rate were conducted on a Gleeble 3500 thermo mechanical simulator, and the constitutive model was developed based on the experimental data. The measured true stress-strain curves exhibited three types of variation patterns, which are (i) a plateau type, (ii) single peak type and (iii) multi peaks type. These patterns well displayed the effects of the deformation temperature, strain rate and plastic strain on the flow behaviour of the bimetal. By incorporating the Zener-Hollomon parameter and material parameter functions of α(ε), n(ε), Q(ε) and A(ε) into Arrhenius-type constitutive equation, the flow stress values predicted by the proposed model show a good agreement with experimental results by the evidence of reproducing true stress-strain curves accurately, high value of correlation coefficient (R=0.9873) and low value of average absolute relative error (AARE=4.81%). The proposed constitutive equation can be used to realise numerical simulation and determine processing parameters during hot-working of the PS/LCS bimetal.