Abstract: Objective: To observe the efficacy of irbesartan/hydrochlorothiazide tablets(IHT) and nifedipine controlled-release tablets (NCRT) in moderate to severe essential hypertension. Methods: Patients were randomly divided into A group(IHT 150 mg,per day, n=21),B group(NCRT 30 mg per day,n=25),C group(150 mg per morning,NCRT 30 mg per night,n=32),three groups were all treated for 12 weeks. Results: Blood pressure of three groups all greatly decreased(P < 0.01),the total effective rate in IHT groups was 61.9%; the total effective rate in NCRT groups was 64.0% the total effective rate in IHT + NCRT groups was 93.8%. Conclusions: IHT plus NCRT are more efficiency than IHT or NCRT group in the treatment of moderate to severe hypertension. So it deserve to popularize fore more efficiency and more security.