Parkinson’s disease is a common degenerative neurological disease of the elderly and is one of the leading causes of disability in middle-aged and elderly people, and there is no definitive way to mitigate the progression and cure the disease. As knowledge of Parkinson’s disease has become more widespread, the manifestations of typical Parkinson’s disease such as resting tremor, slow movements and muscle tonus have been well recognized and valued by the public and doctors. However, when the above symptoms appear, Parkinson’s disease is already in the middle and late stages. Olfactory hyposmia is a common symptom of Parkinson’s disease and is present in 70-90% of Parkinson’s disease patients. It is especially important to note that olfactory hyposmia often manifests 3-7 years before the appearance of the above typical symptoms. The mechanism of early onset of hyposmia in Parkinson’s disease is not yet clear, but it is currently speculated that the earliest possible site of Parkinson’s disease involvement is the structures related to olfaction. Olfactory examination is a sensitive and simple clinical test that can be used as an early aid to identify Parkinson’s disease, but it is necessary to exclude factors that may cause olfactory hyposmia such as combined upper sensory and nasal diseases. Therefore, hyposmia is currently an early warning sign of Parkinson’s disease. If middle-aged or elderly people have newly developed hyposmia, and it is confirmed by olfactory testing, but cannot be explained by other causes, they should beware of the possibility of very early Parkinson’s disease.