Abstract: This research studied the effects of hot rolling parameters on dual phase steel as a hot rolled product. Objective of the research was to determine the influence of different hot roll parameters that affect the microstructure of the rolled steel when it was tested in the conditions similar to hot rolling. These parameters consisted of deformation degree, deformation temperature, holding temperature and holding time at a constant temperature after the test specimen is deformed. These tested parameters affect the morphology and volume fraction of soft ferrite matrix of dual phase steel. The type of morphology and volume fraction of ferrite will lead to different properties of hot rolled dual phase steel. This research used a carbon steel containing manganese-niobium as master specimens. Rolling simulation was conducted with the aid of a deformation dilatometer. Experimental procedure consisted of a development of continuous cooling transformation diagrams of tested steel, investigation of hot rolling parameter on ferrite formation and modeling of ferrite formation. By considering the continuous cooling transformation diagram, the ferrite formation temperature of tested steel is in the range of 650-700°C. The hot rolling simulation at a temperature between 650 and 690°C showed that increasing of deformation degree increased volume fraction of ferrite. This was due to the increasing deformation degree which affected the increasing nucleation site of ferrite and also affected grain refinement of ferrite. Holding temperature and holding time of specimens after deformation significantly influenced the ferrite formation. The test series showed that lower holding temperature and longer of holding time resulted in increasing volume fraction of ferrite. Comparative results obtained from hot rolling simulation using deformation dilatometer and the calculated results using a mathematical model showed similar trends of hot rolling parameter influences on ferrite formation and also shared comparable values. This research therefore introduced a construction of a processing map which presented the relationships among hot rolling parameters and ferrite formation. This processing map could be used for controlling a hot rolling process to obtain a desirable hot rolled dual phase steel.