Through distinction ananlysis against a life cycle observation data which we got from the three inclinometers in the deformation cave of the Changshu Seismic Station.We can find the basement influence and reasons which caused longterms zero drift .And then we can provide the method for the segregation of quantitatively determine and improve the procedure of set up the instrument. Analysis stated that sustained loading of base stone block will produce creep of concrete.The creeping against different thickness of the concrete will lead to base stone block tilt.The process is non-linear. It shows the development of exponentially distributed and run through  the life cycle of the instrument.