Kaylee M. Long, 22, was taken by Life Flight air ambulance to University Hospital in Columbia.
The accident occurred about 2:45 p.m. on state Highway 41 two-tenths of a mile north of Darling Street.
Long was walking north on the right side of the roadway when a truck driven by Matt Dehn, 31, of Marshall, passed her. Part of the load on the truck's trailer struck her, troopers said.
Saline County sheriff's deputies and Saline County Ambulance crews assisted.