In this paper, we investigate the coherent Rabi oscillation dynamics of internal states in ultracold atoms under radio-frequency (RF) phase control. In the experiment, a single Zeeman sublevel of ⁸⁷Rb Bose-Einstein condensate (BEC) was first prepared using an all-optical method. A single RF field was then applied to manipulate the atomic populations between two hyperfine ground states \left|F=1, m_F=-1\right\rangle and \left|F=1, m_F=0\right\rangle of ⁸⁷Rb. By measuring the time evolution of the atomic dynamics, the RF coupling strength was calibrated. Then, two RF fields were employed to couple the two hyperfine ground states \left|F=1, m_F=-1\right\rangle and \left|F=1, m_F=0\right\rangle of ⁸⁷Rb. By measuring the atomic dynamical evolution under different relative RF phases, the dependence of the coupling strength on the RF phase was obtained. The results clearly reveal the controlling effect of the RF phase on the coupling strength and systematically verify the periodic variation of the coupling strength with phase. Continuous and high-precision control of the coupling strength from zero to its maximum value was achieved. Compared with optical phase control, RF phase control exhibits higher stability because the RF wavelength is much larger than the atomic size, leading to reduced sensitivity to phase noise. Moreover, RF phase manipulation enables precision control at the milliradian level. Finally, phase control was used to achieve rapid switching of the coupling strength. Compared with conventional methods based on power modulation, replacing intensity control with phase control improves the switching speed of the coupling strength by one to two orders of magnitude, overcoming the intrinsic limitations imposed by power amplifiers. The introduction of the dual-RF-field scheme further enriches the available approaches for controlling coupling strengths between atomic internal states and provides a new pathway for precise manipulation of atomic interactions. This technique offers a new method for realizing complex quantum-state control and quantum simulation in ultracold atomic systems.