You Do Need power plug adapter while traveling from Swaziland to China.

Here is Why You Need An Adapter

The outlet and plug type used in China are A, C and I and in Swaziland is M. This is how they look like.

Swaziland

In Swaziland, outlets of type M are in use.

Type M

China

In China, outlets of type A, C and I are in use.

Type A

Type C

Type I