 The trial will mainly compare the amlodipine with nifedipine GITS group in the changes of morning blood pressure 4 am-8 am, about 8 blood pressure readings and nighttime blood pressure 10 pm-4 am at 4 and 8 weeks from baseline. The student t test will be used and 95 confidence interval of the differences between the 2 groups will be computed. In addition, an adjusted analysis ANOVA will also be performed while accounting for major baseline characteristics. 