You can use formControlName in <ion-radio-group>
<ion-list> <ion-radio-group formControlName="preferredLanguage"> <ion-list-header> <ion-label> Select Language </ion-label> </ion-list-header> <ion-item> <ion-label>English</ion-label> <ion-radio value="English"></ion-radio> </ion-item> <ion-item> <ion-label>Spanish</ion-label> <ion-radio value="Spanish"></ion-radio> </ion-item> </ion-radio-group> </ion-list>