Dual-direction multi-function well flushing assemble is a special patented well flushing tool for open hole horizontal well completed with sand control liner/screen. In open hole horizontal well completed with sand control liner/screen, the flushing tubing string and other related tools are tripped down inside the liner/screen to implement acid flushing, acid leaching or small scale acidification with formation polluted by drilling mud by means of reverse flushing or flushing. The formation treatment can remove the drilling mud pollution near borehole zone, reduce surface factor in formation, improve formation percolation conditions, and decrease formation energy consumption and increase oil well production.