We adopted phase-contrast MRI to real-time acquire flow velocity information with transmitting focused ultrasound pulses on microbubbles in a flowing phantom. We aim to evaluate the velocity changes resulted from the formation of bubbles by secondary acoustic radiation force. We observed that temporal standard deviation of velocity and %velocity change increased with increasing MBs concentrations. It can be attributed to the formation of aggregated bubbles, which can narrow the chamber diameter and accordingly lead to higher flow velocity. In conclusion, we verified the feasibility of using phase-contrast MRI to evaluate the impact of secondary acoustic radiation force.