Reservoirs in Weizhou Formation of Weizhou11-4N Oilfield have entered the stage of high and ultra-high water cut，and the recoveries of some oil groups have approached or exceeded the measured oil displacement efficiency of existing exploratory wells. In view of the current oil displacement efficiency，reservoirs have less potential to be developed，and studies on the oil displacement efficiency of reservoirs in Weizhou Formation under high-multiple water flooding shall be carried out. According to the above problems encountered in the development，a core water flooding experiment with an injection amount of 200 PV was conducted. A flat visual water flooding model was designed to visually describe the high-multiple water flooding process and the distribution law of residual oil. In addition，nuclear magnetic resonance（NMR）technology was used to facilitate online core water flooding experiments and quantify the oil displacement efficiency in pores at large，medium，and small scales. The experimental results showed that the oil displacement efficiency of long cores reached 73.2%，which far exceeded the currently recognized oil displacement efficiency. When the permeability ratio of long cores in parallel was large，Bernoulli’s effect was proposed for the first time at the inlet end of cores with high and low permeability. During microscopic water flooding，the injected water broke through rapidly along channels with medium and high permeability，and the anhydrous recovery of the model was only 18.6%，and after a water flooding of 200 PV，the crude oil in low-permeability areas was effectively started. The results of online NMR displacement experiments showed the medium pores have contributed the most to the oil displacement efficiency，reaching 45.63%.