Renewable energy is present to overcome the global energy crisis problem. The innovation needed is sustainable alternative power generation. One of the innovations related to renewable energy generation is the Oscillating Wave Surge Converter (OWSC), a Wave Energy Converter (WEC) device that absorbs energy from ocean waves into electrical energy. This research strengthens efforts to explore the ocean’s unlimited potential energy sources. This research focuses on developing the OWSC device to achieve optimal design. In this research, variations in the width ratio to a wave interval period were carried out using numerical methods as an analytical approach. The results of this study show that the effect of changing the width ratio is directly proportional to the performance of the OWSC device. This is indicated by the peak movement displacement occurring at W/H = 3 and the smallest at W/H = 1. Next, what is the peak torque at the W/H = 3 variation and the smallest at W/H = 1, then what is the highest peak mechanical power at the W/H = 3 variation and the smallest at W/H = 1. However, the increase in device performance only occurs at narrow period intervals. This is shown in the width curve W/H = 1, which has a power magnitude in a different period from W/H = 3. This difference in period is caused by the device’s hydrodynamic characteristics, which causes an increase in the width ratio that is no longer relevant at specific intervals. This is shown in the W/H = 3 curve, which experiences an increase in the wave period from 2 s to 2.5 s and then decreases to a period of 7 s.