My Ex-Wife has ben harassing me for about 3 Years.On my voice mail that I have recording of her saying she was going to tell everone that I was having sexual relations with my granddaughter.and place it on Facebook. EX called and left a voicemail on my daughter husband office phone.saying that I was looking at child pornography and sleeping with my granddaughter.what can I do to stop her abuse to me and our family. Every one in the family and I is wonting to file a legal complaint against my EX-Wife I need a good attorney.she is causing me and my family a lot of stress.

Hire a lawyer... this is not a do-it-yourself sort of thing.
Keep those recordings... do NOT erase them. They will be interesting to present as evidence in court. And avoid the temptation to respond to her in that manner that she can record and use against you.

You can find a good attorney, local to you of course. You are asking on a world wide site.
It isn't easy to sue for slander or libel. You can save phone recordings, emails, and so on, but they don't hold up well in court because they can be fabricated (and I doubt that you want to pay for voice identification experts). You have to prove that you suffered losses. I'm not even sure about the phone call to the workplace unless others there heard it, and even then, you don't work there. It's going to be difficult.

I am not positive about Facebook, but I believe that they are responsive to requests to remove seriously accusing remarks. You could contact them in advance. I'm sure your friends and family know about this and have their own minds.

Some of this goes with the territory of divorce. Courts have heard this many times. Often when one spouse starts, the other one counters with equally damaging claims. Whether that might make it worse or better, no one knows. Some hire a PI to dig up any dirt from the past or present.

... EX called and left a voicemail on my daughter husband office phone.saying that i was looking at child pornography and sleeping with my granddaughter. ...

That (the sleeping with grand-daughter allegation, anyway, it's uncertain whether looking at, as opposed to possessing child pornography, is a crime) would be defamation per se (untrue allegation of serious criminal conduct). That means that specific damages don't have to be proven. It's a good question whether leaving a voice-mail is libel ("publication") or slander (spoken to another person), but it probably doesn't make much difference either way. But if I were your attorney I would doubt that a jury would award enough to make it worth my while.

... I'm not even sure about the phone call to the workplace unless others there heard it, and even then, you don't work there. ...

OP found out about it somehow. Chance are that someone heard it and could testify that they heard it.

First off I would file a restraining order barring her from not only contact with you but also from saying anything bad about you. After that then sue if you wish but for the time being you should get some peace.