Abstract: A low-cost voltage relaxation oscillator with high accuracy is proposed in this paper. It uses a dual capacitor alternating charging and discharging structure, so that the high/low level duration of the oscillator's output square wave is only related to the charging time of the reference current on one holding capacitor, and is independent of the discharge time of the capacitor, stabilizing the duty cycle of the output square wave. The charging time of the capacitor is determined by the reference current and the capacitance of the holding capacitor, so the frequency of the output wave has a low temperature drift. At the same time, the oscillator uses a three-input and two-output comparator to control the charging and discharging of the two holding capacitors, eliminating the need for a 1/2 divider circuit, thereby reducing the delay caused by digital logic and maintaining the voltage overshoot of the capacitor, and improving the stability of the oscillator's output frequency. The oscillator is designed and manufactured using SMIC 180 nm BCD process, with an oscillation frequency of 4 MHz and an area of 0.0027 mm². The test results show that when the temperature changes from −40 ℃ to 125 ℃, the maximum measured frequency error is 0.9% and the power consumption is 12.6 μW.