Abstract: Methods and results of foundation improvement, column base re-alignment and jacking up by pile underpinning at the Northwest Rubber Factory, Shanxi are introduced. Results of analyzing eighty-four preloaded piles, fourteen column base re-alignment and fifteen column base jacking up showed that the bearing capacity of the foundation after pile underpinning, the reinforcing effect are reliable, the column base re-alignment and jacking up are successful. It is an effective methods for foundation improvement. From result of test pile method of determining allowable bearing capacity of single preloaded pile is presented. Empirical relationships between pile pressurizing resistance and intermittent time, upward reaction and rebound of top of pile are given. This method has a practical meaning in increasing safety margin and controlling further subsidence of structures.