Objective To study the double chroma ink mapping of Lc & C, Lm & M, and Lk & K, which are commonly used in most multi-color inkjet printers. Methods Based on colorimetric matching， polynomial fitting was used to establish a mapping relationship between every pair of double chroma ink, and the fitting accuracy was contrasted between different fitting times and different printing resolution. Results The maximum color difference of matching points was 14.33 suing two times fitting after low-resolution printing (720 dpi), and that of four times fitting was 4.59. The maximum color difference of matching points was 21.60 suing two times fitting after low-resolution printing (720 dpi), and that of four times fitting was 8.72. Conclusion Experimental results showed that the four times fitting could achieve higher accuracy than the conic fitting, and the mapping accuracy of low printing resolution (720 dpi) was higher than that of high resolution (1440 dpi). The study is of great significance for color separation of printer with two levels of color channel.