Abstract: The Ordovician carbonate reservoir in Tahe oilfield is characterized by strong heterogeneity, developed cavity and fractures as well as complicated distribution influenced by tectonic activity and karstification, which gives rise to big difference between carbonate reservoir and sandstone reservoir development by waterflooding process. This carbonate reservoir is usually developed by such waterflooding process as injecting water into lower reservoir intervals and oil production from higher reservoir intervals, or injecting water into fractured intervals and production from cavernous intervals. However, with the deepening of waterflood development, part of fracture?cavity intervals have occurred poor responses in effectiveness. This paper presents the cyclic waterflooding process using numerical simulation method, and demonstrates the injection?production parameters such as water injection timing, cycle and volume, etc. It is suggested that the water injection timing could be at water cut of 80%, the cyclic injection amounts to 5.1×104 m3, the time of each cyclic injection is 50 d, and intermittent injection process should be used by 30 d for water injection and 20 d for shut?in phase