The invention discloses a capacitor array switching method applied to a low-voltage SAR ADC. An analog-to-digital converter based on the method comprises two N-bit sub analog-to-digital converters with the same structure, the method comprises the following steps: for the input signals VIP and VIN, after N comparisons, obtaining N-bit digital output codes, which are divided into a sampling stage and a conversion stage, wherein, in the sampling stage, the input signals VIP and VIN are respectively connected to top polar plates of an upper capacitor array and a lower capacitor array through sampling switches, and bottom polar plates of all capacitors of the upper capacitor array and bottom polar plates of all capacitors of the lower capacitor array are connected to corresponding voltages; and, in the conversion stage, the comparator performs MSB bit-to-LSB bit comparison on the voltages of the top polar plates of the upper and lower capacitor arrays to obtain corresponding digital codes,and the connection relationship of the capacitor bottom polar plates in the upper and lower capacitor arrays are controlled according to the digital codes, and the N-bit digital output codes are obtained through N times of comparison. According to the invention, the power consumption of the DAC part in the conversion process can be greatly reduced, only two reference levels are adopted, and the method is suitable for the design under the near threshold voltage.