This paper report proposes a technology of dot inversion bipolar grayscale modulation for electrowetting displays to address issues such as oil backflow and grayscale distortion caused by interface charge accumulation during unipolar driving. Based on the bipolar driving characteristics of electrowetting displays, this paper adopts a pixel-level dot inversion strategy, driving pixels with positive and negative polarity voltages periodically to balance the interface charge distribution and suppress oil backflow. Further, a grayscale multiplication driving waveform based on subframe time division multiplexing technology is designed to overcome the reduction in the number of grayscales under bipolar driving, thereby achieving display with the same grayscales level as the driving chip. Experimental results indicate that the proposed technology in this breif can effectively suppress oil backflow. The proposed technology reduces the luminance decay rate ratio caused by oil backflow decreases by 13.72 times, with an attenuation suppression rate of 92.7%. This provides an efficient and compatible driving solution for the industrialization of electrowetting displays.