Based on the principle of double frequency laser interference measurement ofhigh accuracy linear grating. This technique is discussed in detail from two aspots:totol lenth cumu-lative error measurement and Morie fringe signal quality analysis of linear grating.It includes lasersignal processing tochnique, signal sampling,computer interface circuit and related algorithm. withthis methed, we can not only get its accuracy parameter of a linear grating, but aiso analyze the er-ror factors which would affect the accuracy of a linear grating in graving process. In addition,it cancny out dynamic measuremtns for other length metrological elements.