Abstract: The trend extrapolation from theory of grey system to forecast pipeline integrity is recommended in this article, which is based on the uncertainty of integrity data of pipeline, low variety speed, of pipeline environment, little disturbed of data and other information, etc. Principle, classification and others to forecast the researched object are presented as well. The step and method of creating forecasting data series are also introduced, and a practical calculation example is given here which have detection data detected only once.