Hi I just seen the piolt for the next generation and Bones was there, at 137 years old. How did that happen? Did he just not die? Was it ever explained?

Not much was actually explained about McCoy in the "Encounter at Farpoint" other than he was 137-years old and an admiral by that point. In the 24th century in Star Trek lore, humans can live longer. The scene you refer to was actually very touching. :)