Now a day’s COVID-19 becomes a pandemic and corona virus causes severe health issues in human being. The new variant of corona i.e.B.1.617.2 has come into existence in India for the first time and then this delta variant gradually spreads in other countries as well. Many people have also lost their lives because of the delta variant of the virus. Lot of efforts has been done by the government throughout the world to overcome this threat and vaccination has also been made free, so that everyone can be vaccinated In this paper fuzzy rule based model is proposed which predicts whether the patient is suffering from delta variant of COVID-19 or not. To diagnose the delta variant of COVID-19 disease, we have considered ten input factor and the one output factor which depicts the severity level of the infected patients.