The effects of salt， sugar and vinegar as well as ascorbic acid， citric acid， sodium D-isoascorbate and potassium sorbate on color and pigment of Undaria pinnatifida during boiling were studied by using colorimeter and high performance liquid chromatography. The results showed that 0.2% salt provided good color protection and increased the yield of fucoxanthin and chlorophyll a by 29.12% and 79.73%， respectively. The addition of 0.3% sugar and 0.04% sodium D-isoascorbate significantly reduced the chlorophyll a content [(3.36 ± 0.11) μg/g and (9.13 ± 0.73) μg/g， respectively] while improving the color stability of Undaria pinnatifida， which was only 21.51% and 53.02% of the control group. As the ratio of vinegar increased， the Undaria pinnatifida gradually changed to olive color， with a color difference of up to 5.01. 0.025% vinegar resulted in a complete loss of chlorophyll a， while the addition of 0.004% citric acid resulted in a significant increase of 29.53% in the yield of fucoxanthin [(276.51 ± 16.15) μg/g] compared to the control [(213.47 ± 16.77) μg/g]. Ascorbic acid and potassium sorbate had a dual effect on the color stability of Undaria pinnatifida， with low levels (0.004%) of ascorbic acid promoting the retention of chlorophyll a， resulting in a significant increase in the yield of fucoxanthin [(422.73 ± 26.35) μg/g] compared to the control [(201.09 ± 14.42) μg/g]， while high levels (0.10%) of potassium sorbate resulted in a 69.60% loss of chlorophyll yield. In the future development of seasoned Undaria pinnatifida， appropriate proportions of flavorings as well as additives should be added to achieve the desired processing quality traits.