The control of interatomic interactions is crucial in quantum simulation research on many-body physics using ultracold atoms and has emerged as a key mechanism for inducing various physical phenomena. In this study, we explore the competition between atomic interactions and Stark localization in a one-dimensional tilted momentum lattice system of ultracold Cs atoms. Initially, under non-interacting conditions, we increased the lattice tilt F by adjusting the detuning of Raman lasers and measured the dynamical evolution of atoms via time-of-flight imaging. This allowed us to observe Stark localization in the system, which we quantified using the momentum distribution width d. Subsequently, we precisely tuned the interaction strength U among Cs atoms through Feshbach resonance to examine the impact of repulsive interactions on the localization dynamics. The experimental data reveal that the critical point for localization, F_c, decreases linearly with increasing U, dropping from 2.85 at U/J=0 to 1.48 at U/J=2.9. This finding demonstrates that repulsive interactions in momentum space can accelerate the Stark localization process. These results provide new experimental insights into the mechanisms of many-body localization dynamics in systems with long-range interactions.