This paper is concerned with the shear band formation in sheet metal under dynamic loading. The shear band propagation is analyzed by an explicit elasto-plastic finite element code, which adopts the Johnson-Cook model to consider the effect of strain hardening, strain rate hardening and thermal softening. In the analysis, the constitutive equations are integrated over a time step by a modified PPEC method, which calculates the stress accurately in a single step without iteration. The study investigates the effect of the material constants in the Johnson-Cook model on the adiabatic shear band. The results show that the increase of the material constant A accelerates the shear band formation while the decrease of the material constant B, n, C, m accelerates the shear band formation.