Non-distortion is an important aspect in precision measurement, calibration and signal processing. In this paper, the distortion error of a linear time-invariant measurement system is derived for periodical and non-periodical signal inputs, using Fourier Series and Fourier Transformation. The signal distortion is measured by the error-to-signal energy ratio. A charge amplifier circuit has been analyzed as an example, which shows that the distortion of an LTI system can not be simply neglected if precision measurement is required. Direct compensation and adaptive control methods have been discussed to reduce the LTI system distortion. The applications of these two methods to the charge amplifier design are discussed, which demonstrated good results.