Abstract: In this study, headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to determine the volatile flavor compounds of sundried Ulva spp., including U. prolifera collected from Xiamen (sample X), U. linza collected from Yantai (sample Y) and U. clathrata collected from Ningbo (sample N). A total of 61 volatile compounds including 19 aldehydes, 9 ketones, 6 alcohols, 8 acids, 3 esters, 2 sulfur compounds, and 14 other compounds were detected. The content of sulfur compounds was reaching 40.39%~58.09%. Meanwhile, relative odor activity value (ROAV) and sensory evaluation were employed to identify the aroma active components of Ulva spp.. The results revealed that dimethyl sulfide (onion, garlic, sulfur) and β-ionone (violet, floral) were the key aroma active components of dried Ulva spp.. Besides, dimethyl sulfoxide, 4-methyl-3-penten-2-one, benzaldehyde and 5,6,7,7a-tetrahydro-4,4,7a-trimethyl-2(4H)-benzofuranone were the important aroma active components of three Ulva spp.. Among three tested Ulva spp., sample N contained the most abundant volatile compounds especially in aldehydes and ketones, and (E)-2-butenal, (E)-2-octenal, (E)-2,6-nondialdehyde and 1-octene-3-ol were considered as the key volatile substances. Aroma active compounds including 4-ethylbenzaldehyde, (5Z)-1,5-octadiene-3-ol, and 5-methyl furfural were only detected in sample Y, which might correlate to its unique green and fruity flavor. For sample X, the sensory analysis reulst revealed significant fishy smell (P<0.05) as compare to other two Ulva spp., while sample N and sample Y were more inclined to more floral, fruity and fatty green flavor. These obtained results would help to obtain more information of the volatile flavor compounds of Ulva spp. and for further Ulva related product development.