Abstract: Because of poor ground conditions, stoping methods of underhand headings with cemented fill were used in the Jinchuan No. 2 mine, a paste fill system was set up. In order to evaluate the reliability of the new system, investigations and trial running have been done. More than 20 items of modification or improvements related to paste preparation subsystem, pump and pipe subsystem, auto-controlling and monitoring subsystem were finished. The reliability of the paste fill system was analyzed by using the theory of large complex system, and it is useful in reliability study on paste fill system.