The causes of left hand tremor in patients are mainly seen in abnormal thyroid function, Parkinson’s disease, idiopathic tremor, and drug effects, as follows: 1. Abnormal thyroid function: A young patient with left hand tremor in the form of subtle tremor should be asked if there is any change in temperament and personality, how about appetite, whether there is fear of cold, laziness, and also thyroid function measurement to understand whether there is hypothyroidism or hyperthyroidism. 2, Parkinson’s disease: left hand tremor is a resting tremor, also accompanied by increased muscle tone in the left hand, ask the patient whether there is a past history of tremor, or whether there is a family history of left hand tremor, need to be alert to the possibility of Parkinson’s disease. 3, idiopathic tremor: the patient appears left hand tremor, is writing, holding things mainly, consider idiopathic tremor. 4, the role of drugs: the patient appears left hand tremor. The patient should be asked whether he has taken some antipsychotic drugs, whether he has a past history of mental illness, and whether there are some antipsychotic drugs with side effects, mainly hand tremors.