The present disclosure provides an SOI analog front circuit for a medical device, characterized in that it comprises an automatic gain control loop and a 2-order-3-bit-quantization Sigma-Delta analog-to-digital converter, wherein: the automatic gain control loop is configured to implement automatic control of loop gain and output an analog signal to the 2-order-3-bit-quantization Sigma-Delta analog-to-digital converter; and the 2-order-3-bit-quantization Sigma-Delta analog-to-digital converter is configured to convert the analog signal output from the automatic gain control loop into a digital code and output the digital code to a DSP for processing. The analog front circuit for the medical hearing aid device may be implemented by integration of three comparators, an analog-digital hybrid automatic gain control loop and a 2-order-3-bit-quantization Sigma-Delta analog-to-digital converter on a single chip using SOI process with high reliability and low power consumption. The analog front circuit has high accuracy, high reliability, and low power consumption. The analog front circuit may be applied in the medical hearing aid device.