This paper compared the singing voices of four student singers of Chinese national singing before and after vocal warm-up. Statistics showed that the parameters such as deviation from the standard note, vibrato rate and jitter were undergoing significant changes after 30 minutes of warming up exercise, while the differences of vibrato extent demonstrated a controversy result. Overall, this paper indicated that, all of the participants benefited from vocal warm-up by increasing accuracy of singing tone heights, decreasing jitters and approximating their vibrato rates to the moderate range of western singing style.