Some babies do wear diapers in China.
Other babies actually have slit pants that allow the baby to poop and the poop land on the ground.
The baby also usually pees through a hole in their pants as well.
Mostly though the babies that don't wear diapers are babies of really poor families otherwise they either wear disposable diapers or cloth diapers.
Disposable diapers are available in China and they are also widely used in China by the parents who can afford them.
If the parents cannot afford diapers in China then they either wear a cloth diaper which is then washed and cleaned and hung out to dry.
Or the baby wears the pants or shorts with a hole in them.
But the majority of babies in China and toddlers in China do wear diapers whether it be disposable or cloth diapers.