Sinus arrhythmia at the age of 5 is a condition in which the heart has a normal pacing point but beats in an irregular rhythm, and is generally recognized as a common physiological variant in adolescents and children when other pathologic factors are ruled out. In normal people, the heart’s pacing point is in the sinus node, so it is called sinus rhythm. Rhythm refers to the rhythm of the heart beat, the normal human heart rhythm is basically regular, some teenagers and children can appear with the respiratory changes in the heart rhythm, inhalation when the heart rate increases, and exhalation slowed down, called sinus arrhythmia, generally no clinical significance. If 5-year-old children do not have palpitations, shortness of breath, loss of energy, etc., and there is no abnormality after cardiac ultrasound and other examinations, no treatment is needed. 5-year-old sinus arrhythmia is recommended to the regular medical institutions, the relevant examination to detect the existence of pathological factors, need to comply with the doctor’s instructions for targeted treatment.