When my baby sees a new faces throws a lot of tantrums what to do?

It's a very common behaviour.At this age they r not bothered about manners , or how to behave properly with others & at this age for baby new face means strangers .So they will b hesitant to mingle or smile or go near new people.By age 3 or after it this behaviour changes gradually when they mostly c elders at home behaving in a nice way to others & u can tell her small things like smile to others or when ask name she should say it or to say hello to people etc

Darshana is right. Kids can't mingle with new persons. Don't force her to mingle because kids feels insecure or shy. If any new ones come to your house prepare them first like some one is coming to our home and tell their relation and tell how to talk. After some time they wil come and stay normally.
And sometimes kids mingle very fast some kids don't. Let her talk with your family members in phone or directly .

Hi that's behavioural and will improve with growth of baby