Abstract: The response of Peridinium gatunense (formerly Peridinium cinctum fa.westii) to different light regimes was investigated based on pigment profiles, which were revealed by HPLC analyses, over the ranges of 16.6-250μE·m-2·S-1 Peridinin and diadinoxanthin are the two most important carotenoids, shared about 90% of the total xanthophylls.Cellular chlorophyll a showed an evident drop along the increased irradiance gradients.Evidence was presented to show the role of diadinoxanthin and β-carotene as light protectants, including: l) diadinoxanthin / chlorophyll a ratios increased drastically when Peridinium was exposed to increased light gradients and β-carotene / chlorophyll a ratios also showed an obvious increasing tendency; 2) β-carotene / chlorophyll a ratios under light condition were higher than those under completely dark condition; and 3) diadinoxanthin / chlorophyll a ratios exhibited inter-group differences among high irradiance, low irradiance, high to low and low to high irradiance treatments.Hereby the possible implication for pigment metabolic routes and their limnological behaviour was deduced.