My wife had completed 6 months of pregnancy but she still have complaints of morning sickness. She often has vomitings.... Please suggest..

Yes, few mommies do have it for a long time. I had until I delivered my baby. Will tag you an article to help you. Also if too much Nausea talk to your doctor and take meds accordingly.
Vomiting During Pregnancy - A Definite Sign Of Pregnancy
9 Tips For Dealing with Morning Sickness