Abstract: The digital closed-loop quartz flex accelerometer (DCLA) can effectively solve the precision loss which exists in the output current to the digital conversion of the traditional analog quartz flex accelerometer, and the accuracy of the DCLA mainly depends on the differential capacitance detection circuit. The working principle of DCLA was introduced, and the signal detection scheme was studied. According to the signal characteristics, with the method of single carrier modulation and demodulation technology, triangle wave modulation technique was applied to implement the capacitance detection, and the digital correlative demodulation scheme was proposed to extract the amplitude signal. To build the DCLA experimental prototype, under the 0 g/1 g stability test, the bias stability of 0 g/1 g was 17.595 0 g, 19.363 7 g and 20.715 3 g, respectively. Currently, the result shows that the precision of the DCLA is basically equal to the traditional analog accelerometer, which verifies the correctness of the signal detection method.