The invention provides a seven-color color separation model construction method based on a polynomial regression algorithm, which is used in a multi-color color separation method and is characterized by comprising the following steps: 1, designing a test sample set, dividing cyan, magenta, yellow, black, red, green and blue into six groups according to hue angles, performing balanced sampling according to the dot area rate of each color to generate a test sample set, and printing and outputting the Lab color value of the test sample set through a multi-color printer; 2, taking the dot area rate of each color block in the test sample set as a dependent variable, taking the Lab color value of each color block as an independent variable, and establishing a polynomial regression model; 3, conducting parameter estimation on the polynomial regression model through a total least square method, obtaining all coefficients of the polynomial regression model, so that a seven-color color separation model based on CMYKRGB is established, wherein parameter estimation of the total least square method is shown in the specification.