This paper reports a novel flexible fractal microelectrode integrated with the catheter to achieve diagnosis and treatment for low-voltage pulsed field ablation (PFA). The fractal design increases the ratio of the edge length to the geometric surface area of the electrode, which contributes to the transfer of current from the electrode into the tissue. Besides, the fractal structure reduces the spacing between the electrodes, which can obtain a large electric field. Pt-Black coating enhances the electrical stimulation and electrocardiogram (ECG) recording capability. Foremost, it achieves in vivo ablation at 100 V on rat hearts. In short, the device can perform ablation procedures independently, including low-voltage PFA and ECG recording.