The crash happened shortly after 6 a.m. near 126th Street East and Avenue V-10, authorities said.
The school bus was traveling eastbound on Avenue V-10 and struck the pedestrian, who walked in front of the bus, Antelope Valley CHP officials said.
The woman suffered major injuries and was transported in an ambulance in critical condition to Antelope Valley Hospital.
Authorities said the bus driver was cooperative and released under own recognizance.
There were 10 students on the bus at the time of the crash. Authorities confirmed none of them were injured.
The cause of the crash remained under investigation.