Can we give divorce at once with out any witeness? Or its compulsory in writing?

A divorce is a judgment of law and will be in writing. The complexities and specifics involved in the process depend on the laws of your particular jurisdiction and how they relate to your specific circumstances.

The particulars can agreed upon using mediation here in Canada, this is when neither side needs a lawyer to discuss the dissolving of assets, you meet with a court mediator and then decide who gets what. Afterwards you jointly file a motion for Divorce and poof it's done. Note however that this is only for amicable divorces, if you have kids and property/assets that you can't agree on - that's when it gets expensive... lawyers will get it all.