The optical defocusing projection can produce low-pass filtering and decrease the high-frequency components of the binary grating.So the binary grating is used to produce sinusoidal fringe grating by defocusing projection in phase measuring profilomet ry (PMP).And the Gray-coding light sequence is projected to evaluate the orders of the wrap ped phases for phase unwrapping.However,the changes between the white and black fringes in th e Gray-coding pattern become blurry under defocused projection,which would cause some errors in the binaryzation and make some mistakes in decoding the encoded light sequence.Bas ed on the complementary Gray-coding light,a phase-unwrapping method is used for the def ocused binary grating in this paper.Two kinds of Gray-coding modes are projected onto the me asured object,and the positions of the error words are different.So the two modes are complementa ry,and can avoid the influence of error words on the phase unwrapping.A steep object is success fully measured by this method.Its mean relative error is no more than 1.03%,peak-val ly (PV) error is 0.24rad and the root-mean-square (RMS) error is 0.14rad.The presented method improves the phase unwrapping accuracy,and extends the measure ment range of the defocused binary grating profilometry.It is promising in measu ring the 3D shape of the steep or discontinuous objects.