The variation of the rotor slot geometry causes diminution of joule losses, noise and vibrations, which improves Induction Motor IM performance and efficiency. In this paper, we propose a comparative study of the two IM design structures by varying the slot shapes based on the Finite Element Method (FEM). This software is used to estimate the magnetic field density, the magnetic flux and the harmonic current densities Simulation results prove that the optimal form of rotor slots is the round shape since the gain in torque ripple peak to peak may reach 40% compared to rectangular one.