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The satellite navigation system can provide high-precision navigation, positioning and timing services for all kinds of users around the world. Navigation signal quality is an important factor affecting system service performance. The transmission channel of navigation load has non-ideal characteristics, which will cause the change of navigation signal amplitude frequency characteristic and phase frequency characteristic. Therefore, the channel characteristics need to be compensated by means of pre-distortion. BDS-3 satellite is equipped with a pre-distortion filter in the digital segment. However, due to the limited resources on-board and the low accuracy of broadband pre-distortion algorithm. It is difficult for the navigation signal quality to converge to the index range in the process of pre-distortion adjustment. A piecewise high-precision predistortion method based on spaceborne digital filter is designed. Based on the existing parameters of the wideband filter, the pred-istortion compensation is carried out dynamically and elaborately according to the weights and adjustment requirements, which makes the key indexes of attention converge with higher precision. This method has been verified by 20 satellites in orbit and is an important technical means for in-orbit navigation signal quality optimization.