A phase-unwrapping method based on dual-frequency colorful fringe projection was proposed to improve measurement speed. Only one frame image was collected to realize phase-unwrapping in high-speed measurement and dynamic object contour measurement. The dual-frequency phase measurement and the principle of unwrapping with variational precision were discussed, and then factors affecting measurement precision were analysed in detail. A dual-frequency dual-color sinusoidal fringe pattern encoded by computer was projected by a liquid crystal digital projector. And two monochroic fringe patterns were analysed by Fourier transform to obtain height information of the measured object with high and low precisions and then carry out the unwrapping with variational precision. The results showed that the measurement speed and the unwrapping precision were improved. The maximal absolute error was +1.413～-1.582 mm, and the standard deviation was 0.363 mm.