Treatment method for promoting growth of phaeodactylum tricornutum and accumulation of fucoxanthin

The invention discloses a method for improving growth of phaeodactylum tricornutum and accumulation of fucoxanthin, which comprises the following steps: after the phaeodactylum tricornutum is amplified to a certain number of cells in a logarithmic phase, performing inoculation propagation on the phaeodactylum tricornutum according to a certain proportion, inoculating the phaeodactylum tricornutum to a culture medium containing melatonin and arginine, and culturing the phaeodactylum tricornutum to obtain the fucoxanthin. The method comprises the following steps: culturing phaeodactylum tricornutum in two stages, adjusting the illumination intensity under the condition of red light with a characteristic peak in a wavelength range of 620-700nm in the first stage (0th-6th day) and under the condition of combination of blue light with a characteristic peak in a wavelength range of 430-490nm and green light with a characteristic peak in a wavelength range of 500-580nm in the second stage (7th-14th day), and optimiz