In this paper, we investigate the formation of a photonic terajet and tune its optical properties using the high-resolution finite-difference time-domain method. A Dirac semimetal is coated onto the surface of a dielectric rod and illuminated with an incident plane wave. The refractive index of the Dirac semimetal can be modulated by changing its Fermi energy. It was demonstrated that the presence of the Dirac semimetal layer can significantly affect the characteristics of the photonic terajet, such as focal distance, intensity, full-width at half maximum, and length.