A man has been charged in relation to the death of a pedestrian in Sydney's south west.

Police say a Toyota Corolla was travelling west on Sandringham Drive, Cecil Hills around 5.40pm on Sunday when it left the road and hit an 80-year-old man who was on the footpath.

The pedestrian sustained serious injuries and died on the way to Liverpool Hospital.

The 18-year-old man driving the hatchback, as well as his female passenger, were both uninjured.

The man was taken to Liverpool Hospital for mandatory blood and urine tests. He was later charged with dangerous driving occasioning death and negligent driving occasioning death. 

He was granted conditional bail and will appear at Liverpool Local Court on February 14.

With AAP