Abstract: This paper used the potato as material, optimized the pretreatment method, improved measure method of the amylose and amylopectin, completed the potato starch analysis method.Standard material of amylose and amylopectin was used to draw the standard curve.Five samples, including no desugar and no degrease, degrease, desugar, desugar first than degrease, degrease first than desugar, was used to analysis the content of amylose and amylopectin. The result showed that the maximum absorption wavelength of amylose and amylopectin was 609 nm and 546 nm, reference wavelength was 473 nm and 734 nm, respectively.The coefficient of standard equation regression was higher than 0.999.The sample of degrease first than desugar had good solubility, the content of amylopectin and amylose was 70.27% and 12.38%, respectively. So the degrease first than desugar was a good pretreatment method, which can be accuracy analysis the content of amylose and amylopectin at the dual-wavelength.