The important roles of servo valve zero flow gain, zero pressure gain, zero flow pressure gain coefficient and zero position internal leakage were analyzed, the test curve of the servo valve was used to show that the wear of the sharp edge of the valve core and valve sleeve was the main reason for the decline of the servo valve zero position characteristic and the increase of the leakage flow in the zero position. According to different working conditions, changing the position of the servo valve with poor zero position characteristics can not only reduce the cost of equipment maintenance, but also ensure the performance of the servo hydraulic system and product quality.