how do I prepare tri buffer from its saline [tris [hydroxy methyl] amino methane ],to be use surrounded by electrophoresis.

the electrophoresis machine within which the tris buffer is used is meant for running 'genotype test' within a diagnostic laboratory. If you are referring to the production of agarose or acrylamide gels for separating DNA fragments, next the buffer that you will likely have need of is either "Tris-Acetate" (TAE) or "Tris-borate" (TBE). In any case, the Tris buffer is counter-bablanced by the presence of any the acetate ion or the borate ion. For electrophoretic runs that must go for several hours, TBE buffer is normally preferred because it does not tend to "fail" during longer, higher area strength electrophoresis runs.
If you want to see some recipes for these buffers progress to:
http://www.thelabrat.com/protocols/reage.