3mons old baby need to get visa before going to china?

Yes, your baby also needs a visa to enter China. His/her visa requirements are almost the same with you (I cannot tell the detail since I don't know what kind of visa you are going to apply). Since she/he is under 18 years old, there is no need to provide original NBI clearance and bank statement. BTW, the baby can share a passport with you.

thank you david
if my baby and i can share a passport how about if my baby is carrying his father's last name(surename)?
the father of my baby and i are not yet married that's why my baby's last name is different from my last name.how about that?do i need to get passport for my 3months old baby?thanks a lot

You need to get a passport for your 3 months old baby, you can get a separate passport for him/her or make him/her share a same passport with you.

It doesn't matter if your baby carry his father's last name.