The differentiation of primary hypertension from secondary hypertension relies on ancillary tests, including laboratory tests and imaging. Primary hypertension is a type of high blood pressure of unknown etiology, which may be related to genetics, obesity, hyperlipidemia and high salt diet. The diagnosis is confirmed when secondary hypertension is ruled out. Secondary hypertension is elevated blood pressure caused by diseases such as primary aldosteronism, pheochromocytoma, acute and chronic glomerulonephritis, nephrotic syndrome, and renal artery stenosis. In addition to taking a medical and family history, the differential focus between primary and secondary hypertension requires relevant tests. The common ones are renin, angiotensin and aldosterone ratio, renal artery ultrasound, abdominal CT, cortisol rhythm measurement, renal function tests, urinary protein, urine routine and so on. It is recommended that patients go to regular hospitals, improve relevant examinations under the guidance of doctors to determine whether it is primary or secondary, and then carry out conventional treatment. Generally speaking, after removing the cause of secondary hypertension, blood pressure can usually return to normal.