Principles of antihypertensive drug combination include: different antihypertensive mechanism, produce synergistic effect; reduce the dose of a single drug; reduce adverse effects; eliminate compensatory effect; similar mechanism of action or the same adverse effects should not be combined application. 1. Application of antihypertensive drugs with different mechanisms of action can produce better synergistic effects, such as diuretics and β-blockers combined. 2. Combined use of drugs, reduce the dose of a single drug, improve patient tolerance and compliance. For example, hydrochlorothiazide in more than 25mg per day has adverse effects on metabolism, in the joint use of drugs, small doses can play a synergistic with other drugs. 3. Make different drugs complement each other to reduce or offset adverse effects, such as β-blocker has the effect of slowing down the heart rate, calcium channel blocker can lead to ankle edema and accelerate the heart rate. 4. Combine two antihypertensive drugs to eliminate the “compensatory effect”. When the blood pressure drops, the body will often produce a reaction to prevent the blood pressure from dropping further, which is called “compensatory effect” in medicine, the appropriate combination of drugs can eliminate this compensatory effect. 5. If the adverse effects of two antihypertensive drugs are the same or similar, they should not be used in combination. The combination of two potassium-excreting diuretics, such as hydrochlorothiazide and indopamine, can cause severe hypokalemia. Clinically, professional doctors should adopt appropriate combinations and formulate individualized plans according to the actual situation of the patients, such as the degree and type of hypertension, concomitant factors, and the damage status of the target organs, etc., in order to achieve the best results.