Since MRI has been used in clinical practice, no clear harm has been found to the examinees and the examiners, but with the continuous increase of MRI strength and the emergence of new technologies, so the biological effects of MRI on human body are getting more and more attention. The biological effects of the near magnetic field are mainly manifested as dizziness, headache and weakness after long-term work, but they do not cause irreversible damage to the human body. 2. the biological effects of the gradient field are mainly the most common stimulation of the nerves or muscles around the examinee, manifested as numbness, involuntary muscle contraction or throbbing. 3. The biological effect of RF pulses is mainly the absorption of RF energy by human tissues leading to an increase in tissue temperature.4. The effect of noise on the human body is basically negligible.