Abstract: 20 million t/a phase Ⅲ project of Sijiaying Iron Mine is the largest underground mine in construction at domestic.Through the integrated techniques of ventilation optimization of multi-stage station，optimization of the station，and computer networks resolving，many problems in ultra-large underground mines are resolved such as small air volume，unreasonable air distribution in the system，lack of ventilation，unreasonable settings of stations and selection of fans.All these provide a reliable technical security for the safe and smooth construction of phase Ⅲ project of Sijiaying Iron Mine.

Key words: Ultra-large underground mine, Multi-stage station, Separate ventilation, System optimization