Renin is secreted by glomerular parietal cells as a protease, which regulates the secretion of angiotensin and aldosterone in the body through the renin-angiotensin-aldosterone system. It plays an important role in maintaining the body’s water-electrolyte balance, and is especially important for the regulation of human blood pressure. The normal value is 1.0-2.5 μg-L-1/h. Elevated renin activity is usually seen in primary hypertension with high renin type, glomerular tumor, adrenal cortical tumor, adrenal medullary lipoma and other diseases, while decreased value is seen in primary hypotension with low renin type, aldosteronism, and substantial kidney injury. Before the renin activity test must control the intake of sodium and potassium elements, the daily intake of sodium and potassium must be quantitatively no more than 80 mmol, otherwise it will affect the test results. There are also drugs such as glucocorticoids and licorice taken before the test can lead to inaccurate renin activity test results.