Cardiac ultrasound error less than 3mm is considered normal. If the error is too large, it is easy to cause clinical misdiagnosis. Cardiac color ultrasound can dynamically display the structure of the heart chambers, heart beat and blood flow, mainly detecting the morphology of the heart and whether the heart function is normal. The test results may be affected by the doctor’s measuring habit and angle, the sensitivity and sensitivity of the instrument, and the patient’s cooperation, and there is a certain degree of error. An error of less than 3mm is considered normal. Cardiac ultrasound can be used as a diagnostic basis for tricuspid valve insufficiency, cardiac insufficiency, left ventricular wall motion abnormality, atrial septal defect, etc. If the results of multiple cardiac ultrasound tests are different, it can be combined with other examination items for comprehensive analysis. If patients feel unwell, they should consult a doctor in time to clarify their condition under the doctor’s guidance.