A phase subdivision of absolute coding is proposed to enhance the resolution of absolute coding grating in displacement measurement.The used grating consists of multiple code-channel grating of Gray Code,and the basic code-channel is high-frequentcy Roche grating.Fourier transform method is adopted in decoding,and the wrapped phase distribution of basic code-channel is obtained by Fourier transform,filtering,and inverse Fourier transform,then the unwrapped phase distribution could be obtained using rank inf...