The angle-sensor is a capacitive sensor based on quartz material. In the production process, some products appear obvious zero offset phenomenon under vibration condition. It causes the product to be unqualified, therefore carries out the improvement design to its process. By analyzing the working principle of the sensor, the fault tree model was established, and the cause of zero offset of angle-sensor was determined. The displacement of the sensitive component inside the sensor occurs after vibration, which results in the change of the detection capacitance and leads to the deviation of the zero position output of the sensor. The product assembly fixture has been redesigned, the digital pressure monitoring system has been introduced, and the assembly process has been optimized. After sensor production and test verification, the zero offset fault of the product disappeared, verified that the fault location is accurate, the new process improvement design is reasonable.