An improved phase unwrapping method is proposed in order to reduce the projection fringes and improve the measurement speed in three dimensional(3D) surface measurement.Color fringe patterns are generated by computer encoding with sinusoidal fringe and stair phase fringe patterns in red and blue channels .These color fringe patterns are projected onto the tested objects by digital-light-processing (DLP) projector.The deformed fringe patterns are capt ured by a color CCD camera.Then,the recorded fringe patterns are separated into their RGB components,and 2groups of four step phase shifting fringe patterns are obta ined. One group of the stripe is four sinusoidal pattern,and the wrapped phase is dete rmined by four-step phase shifting method.The other group of stripe is four ste p phase shifting stair phase fringe,whose stair changes are perfectly aligned with the d iscontinuities of sinusoidal fringe phase,which is used to determine the fringe order for the phase unwrapping.The self-correction method is applied to eliminate the noise of fringe order.Finally,the experimental evaluation is conducted to prove the validity of the proposed method.The results are analyzed a nd compared with those of the method by reference(14).The results are s imilar to those of the four-step phase method.But it needs only 4f ringe patterns,can effectively reduce the number of fringe projections and impro ve the measurement speed.