Objective To compare therapeutic effect of Losartan and hydrochlorothiazed compound prepara- tion and Losartan in patients with mild to moderate hypertension and to conduct economical evaluation. Methods The trial began with 2 weeks lead-in period and followed by 8 weeks therapy. 99 cases of mild to moderate hyperten- sion were randomly divided into two groups: compound preparation group ( n = 50) and Losartan (n = 49). The pa- tients were given Losartan 50 mg/h ydrochlorothiazed 12.5 mg compound preparation and Losartan 50 mg ,once a day. If the SeDBP≥85 mm Hg at 4th week, Losartan was added to 50 rag. Results After two, four and eight weeks treatment, systolic blood pressure and diastolic decreased obviously (P < 0.01 for each) ;The overall effective rate of of antihypertension was the same in both groups, but the different ratio of availability and validity in two groups was significant ( P < 0.05 for each). Conclusion Losartan/hydrochlorothiazed compound preparation has significant advantage in improving both systolic and diastolic pressure compared with monotherapy of Losartan. In ad- dition, the patients receiving compound preparation are well tolerated, with higher compliance.