The invention relates to a culture method for improving the mycosporine-like amino acid content in porphyra umbilicalis. The method is characterized by including the following steps that 1, the vigorously growing porphyra umbilicalis is collected, screened and cleaned, is subjected to irradiation with ultraviolet rays with the wavelength of 254 nm for 3-10 minutes for sterilization and serves as a culture object; 2, the porphyra umbilicalis obtained in the step 1 is put in a piping type algae cultivation pool for seawater culture, the temperature is controlled to 20-35 DEG C, the pH is controlled to 5.6-6.4, multiple light sources consisting of an ultraviolet light lamp, a purple light lamp, a green light lamp and a yellow light lamp is adopted to perform continuous irradiation culture for 3-5 cycles, air is pumped in the culture process to keep the porphyra umbilicalis in a suspended state, possibly existing hybrid algae is periodically observed and removed to make the porphyra umbilicalis grow continuously, collection and air-drying are performed after the length of upright branches reaches 4-5 cm, and an amino acid analyzer and UHPLC are adopted to detect the MAAs content of the dried porphyra umbilicalis. The culture method is low in production cost, and the MAAs content of the cultured porphyra umbilicalis is increased remarkably.