To explore the effects of different rehydration ratios on the aroma of yeast powder， and to provide data support for the application of yeast powder in food production. Methods: Sensory evaluation， electronic nose and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) were used to systematically analyzed the odor preference， overall odor fingerprint and volatile compound composition of the samples by sensory evaluation， electronic nose and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Results: The sensory evaluation results showed that yeast powder powder (unrehydrated sample， YN0) had the highest preference. The YN1 sample with a low rehydration ratio (mwhole yeast powder∶mwater=1∶1) had the lowest preference， and its adversed aroma intensity such as sour， sweaty and fermentation was higher than that of other samples. The YN2 (mwhole yeast powder∶mwater=1∶2)-YN6 (mwhole yeast powder∶mwater=1∶6) samples with a high rehydration ratio showed small differences among themselves and were all superior to YN1. The results of electronic nose analysis showed that the clustering trend of the samples was consistent with the sensory order， and sulfides and aromatic compounds were the key differentiating factors. The results of HS-SPME-GC-MS showed that the number of volatile compounds detected in yeast flour increased significantly (from 22 to 64， P < 0.05)， and the content of volatile compounds in the samples with low rehydration ratio (YN1) was significantly higher than that of other rehydration ratios (P < 0.05). After rehydration， the content of acids (acetic acid， isovaleric acid， etc.)， sulfur-containing compounds (methylmercaptan， etc.)， p-cresol， indole， benzaldehyde， etc. in yeast powder enhanced the undesirable aroma components such as sweat， sour， meaty， fermentation， and bitter almonds in yeast powder. Conclusion: Rehydration， especially the low rehydration ratio， played an important role in the release of undesirable aroma components in yeast powder.