The invention relates to a comparator module and successive approximation analog-to-digital converter. The comparator module is applied in the successive approximation analog-to-digital converter and used to make a comparison between the first sampled signal of the first input signal of the successive approximation analog-to-digital converter and the first reference signal in order to get a comparison signal. The comparator module comprises the first comparator, and the first sampled signal will be inputted from one input end, the first reference signal will be inputted from the other input end which will output the first comparison signal. The inverter module is connected with the first comparator's output end, inputting the first comparison signal and outputting comparison signal. According to implementation of the invention, the comparator module is changed into the structure in which the comparator is connected in series with the inverter module, reducing working voltage and power dissipation of the comparator module in the switching circuit of successive approximation analog-to-digital converter and enabling the circuit to work normally in the system with extremely low power supply.