In order to solve the problems of zero position, linearity drift and field calibration difficulty caused by the environmental impact of the depth sensing signal of a small underwater vehicle, an improved sensing signal processing method integrating software and hardware with pure software is proposed. This method is mainly based on embedded processor and digital potentiometer, and uses high-order low resistance digital potentiometer to adjust the gain and zero position of operational amplifier. Combined with the corresponding algorithm, it can not only automatically realize the adaptive adjustment of the output signal of the depth sensor with large individual differences, making its linear amplification output range stable, but also has the functions of scalable digital output, real-time internal recording and convenient on-site calibration. The output signals of different batches of depth sensors can be adjusted to linear output in the range of 1V ~ 5V, so as to solve the problem of inconsistent linear interval of post-processing output caused by individual differences of different depth sensors. At the same time, the hardware zeroing method also avoids the limitation of the adjustment range caused by the conventional software zeroing method, and even greater error caused by exceeding the linear region of the sensor. The actual navigation test shows that the accuracy of the method can be improved by about 2.2m under the water depth of about 100m in an inland lake.