A new fast and robust phase-codeing-unwrapping algorithm is proposed. By alternating the center area of fringes, the code information is added to the phase-shifting fringes, which include not only the primary phase information but also the code information for phase unwrapping. An alteration function is constructed to catch the code information and then give the unwrapped phase. The error and noise of the alteration function is discussed, then a new filter method called directional filtering is proposed to remove the noise, and the mistakes of phase unwrapping are depressed by this method. The simulation and experimental results show the feasibility of the new algorithm. The speed and dependability of the new algorithm are much better than those of the traditional method.