Echelle grating is a kind of special diffraction grating. Working with high diffraction orders and big diffraction angle, which has the advantages of high resolution and full wave shining. It has been widely used in high-end spectrum instrument, which greatly promoted the development of aerospace, astronomy, medical, military, environment and other cutting-edge technology. However, professional scoring system needs to be customized, and the price is very expensive. The use of sophisticated ultra precision machining equipment to process in the ladder grating can greatly reduce the preparation cost of the mother plate of the ladder grating. Due to the bad straightness and high accumulative error of ultra precision single point diamond lathe, it can’t satisfy the demand of preparation when preparing the echelle grating, casuing the bad diffraction wave front. In order to reduce the straightness error, this paper comes up with the error compensation for the single point diamond lathe. Firstly, we make the first compensation based on the accumulative error curve. When the compensation ratio is 0.75 to 0.85, the peak valley value (pv) of the diffraction wave front is about 400 nm, reaching its greatest effect of the first straightness compensation. Secondly, we make the straightness compensation according to the diffraction wave front curve of the blazed order. The pv of the diffraction wave front is about 83nm. The results show that the diffraction wave front is greatly improved which is beneficial to improve the quality of the grating, and has a guiding role in the actual grating characterization.