Mycosporine-like amino acids(MAAs)found in marine organisms,especially in the algae were a class of ultraviolet absorption substances.To study the constituents and proportion of MAAs from Gracilaria changii of Zhanjiang,MAAs were separated and purified by C-18 Sep-Pak SPE and semi-preparative HPLC.Four mycosporine-like amino acids were found and were identified as palythine,shinorine,palythinol and porphyra334,with an approximate ratio of 4.9∶1∶1.2∶9.9,based on the characteristics UV absorption and spectral data.This paper compared the accuracy of UV and HPLC determination for the content of porphyra-334 which was the main component of G.changii, and established fitting curves of two methods.Verified by experiment,the HPLC detection for the main components of MAAs was ultimately determined.This research laid the foundation for the development and use of the UV radiation and anti-oxidative substances in the economic algae produced in our country.