Abstract: In order to solve the low backfill rate problem occurred in the open type backfill mining process with the ultrahigh water material when the inclination of t he seam was low, the theoretical analysis and the site practices method were applied to optimize the traditional open type backfill technique with the ultra high water m aterial.With the site observation, the measures to lift the backfill liquid level were conducted to improve the backfill rate and the gateway retained along the mining gate way and the regional backfill technical measures were applied to improve the backfill rate secondly.With the mine strata pressure observation of the coal mining face, th e mine gateway deformation observation and the surface ground subsidence observation conducted, the technique could release the mine strata pressure behavior inte nsity and could highly reduce the surface ground subsidence and the gateway deformation.