A simple design and small size liquid crystal drive circuit is proposed in this paper. The circuit includes an RC Schmitt oscillation circuit and an inverter. Through a specific connection method, the function of driving a liquid crystal device using only a DC signal within a certain voltage range is realized. Through theoretical analysis and experimental test, the influence of component values on the output waveform characteristics of the circuit is discussed. The test results show that the inverter circuit has a response speed of less than 0.4 μs. The power consumption is less than 1 mW when the input voltage is below 3 V. The input and output voltage have a good linear relationship, which can realize precise control of the transmittance of the liquid crystal device. This research provides new technical ideas for driving liquid crystal devices in miniaturized smart wearable devices.