Wireless sensor nodes deployed at remote and inaccessible locations need long lifetime power sources to prevent cost prohibitive periodic replacement. In this work, we present a radioisotope 63Ni energy converter using radioisotope-powered electrostatic vibration-to-electricity conversion. Free damped vibration happening in a suspended parallel plate structure with a mass enables a variable capacitance, which can be used to realize the generation of electricity energy by an external circuit. The MATLAB/Simulink is used to simulate the vibration and output power, and the Ansys is used to optimize the structure design. The results show that the optimized design structure with a first-order natural frequency of 500 Hz, a plate gap of 75 μm, and an external resistance of 90 kΩ can generate an average output power of 0.416 μW and conversion efficiency of 8.25%.