I want to apply for Phd. program. I am wondering should I write about my high school and personal life in my phd SOP? Or should I keep it on my research objective etc.

I don't think many people care about high school in a PhD application.

Stick to why you want the PhD, and the technical and personal attributes you can bring to the project.

My PhD sop was restricted to 600 words. This scared the life out of me as i write too much (I am learning not to!). In the end I included my research experience (from my Masters), why I believed the research deserved to be done, why I should be the one to do it. I also commented upon why the uni and faculty would be suitable for my research and specific supervision. As opposed to my Masters sop, in which I included everything, and it was about three times as long!
Good luck!