In this work was studied the influence of the plastic deformation's intensity under deep drawing on microstructures of a pearlitic steel containing 0.8% C. Varying the levels of deformation causes diverse dislocation movements as well as modified structural states in the individual phases of the pearlitic eutectoid steel. It is shown that in the course of plastic deformation there is a reduction of interlamellar distance in a pearlite and increase in dislocation density. In some parts partial spheroidisation cementite plates is observed. The bands formed in dislocation structure are found out. The analysis of failure mechanisms of steel with pearlite structure after plastic deformation is carried out. During the deformation of pearlite, the increase in stress at the phase boundary, owing to the elastic strain incompatibility between the ferrite and cementite phases, resembles the stress concentration at grain boundaries. Pores form at the interface between the surface of the ferritic matrix and the spheroidised carbide particles. Such micro pores occur by means of plastic deformation of the ferrite's interstices around the stronger cementite owing to the reduction of the ferritic interstices and their subsequent cracking.