Terahertz (THz) imaging technology has demonstrated significant advantages and potential applications in various fields. However, its further application is hindered by relatively low spatial resolution. The terajets effect, produced by dielectric structures, presents a promising avenue for super-resolution THz imaging. However, the short terajets produced by existing structures present difficulties in both practical and experimental applications. In this study, we introduce a novel approach to generate tunable long terajets using optical elements based on quadratic Bézier curve designs. Numerical simulations indicate that tuning the control point’s positions of the quadratic Bézier curve can lead to diverse variations in terajets characteristics, including a range of maximum intensity (15.17–280.689 V2/m2), focal length (2.664–13.317λ), effective length (4.021–26.802λ), and full width at half maximum (0.383–0.662λ). These findings highlight the tunable potential of this novel optical element, which could significantly improve the resolution and flexibility of terahertz zoom imaging.