The invention discloses a compound drug, particularly relating to a compound antihypertensive drug and a preparation method thereof and belonging to the field of medicine technology. The compound antihypertensive drug is prepared by the following bulk drugs according to parts by weight: 2 parts of hydrochlorothiazide, 1.5 parts of dihydralazine sulfate, 2 parts of promethazine hydrochloride, 5 parts of rutin, 2.5 parts of chloroquine phosphate, 30 parts of potassium chloride, 1 part of thiamine hydrochloride, 1 part of pyridoxin hydrochloride, 0.03 part of reserpine, 30 parts of magnesium trisilicate, 2 to 5 parts of starch, 0.1 to 0.8 part of magnesium stearate and 10 to 30 parts of starch slurry. The compound antihypertensive drug generates low fluctuation of blood pressure in the process of reducing blood pressure for hypertension and the compound antihypertensive drug is also characterized by excellent treatment effect, low side effect, high treatment efficiency and long-lasting drug effect.