Abstract: Pyropia yezoensis exhibited the characteristic of multiple harvests, and its quality was closely associated with the harvest period. Odor serves as a crucial criterion for evaluating the quality of Pyropia yezoensis. To investigate the mechanism by which harvest period affects the odor of Pyropia yezoensis, headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was utilized, with cyclohexane used as the internal standard, to determine the volatile organic compounds (VOCs) that contribute to the odor of Pyropia yezoensis from the first to the fifth harvest period. Simultaneously, an electronic nose was employed to detect the odor profiles of Pyropia yezoensis at different harvest periods. The obtained data were then subjected to principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA) for in-depth exploration. The results indicated that 49, 42, 40, 52 and 47 kinds of VOCs were respectively detected in the first to the fifth harvest Pyropia yezoensis. In total, 71 kinds of VOCs were identified. These VOCs mainly consisted of hydrocarbons (18 kinds), aldehydes (24 kinds), and ketones (10 kinds). Benzaldehyde, safranal, β-cyclocitral, β-ionone, epoxy-β-ionone, α-ionone, 3,5-octadien-2-one, 1-octen-3-ol, dihydroactinidiolide, 8-heptadecene, eicosane, and 1-bromo-5-heptadecene were the common and relatively high-proportion VOCs in Pyropia yezoensis at various harvest periods. The variations in the relative contents of VOCs among different harvest periods of Pyropia yezoensis mainly stemmed from 8-heptadecene, eicosane, dimethyl sulfide, 1-bromo-5-heptadecene, β-ionone, nonanal, (E)-cycldodecene, α-ionone, pentadecanal, 3,5-octadien-2-one, epoxy-β-ionone, dihydroactinidiolide, hexanal, and octanal. The odor characteristics of Pyropia yezoensis encompass floral, fruity, woody, grassy, and fishy notes. Specifically, the odor of first-harvest Pyropia yezoensis is more intense, the fishy odor of third-harvest Pyropia yezoensis is milder, while fourth-harvest and fifth-harvest Pyropia yezoensis exhibit more unpleasant odors, such as the pungent odor associated with lipid oxidation, as well as the characteristic sulfurous and fishy odors imparted by dimethyl sulfide. The electronic nose was basically capable of discerning the odor differences among first-harvest to fifth-harvest Pyropia yezoensis.