Is it possible to re-export materials through land transportation from KSA to UAE for the goods received as import shipments from china?

No , you can not you have to reexport it from the ksa customs to china  if  it inside the borders of the customs but if  you clearance it you can sent it by the transportation to the uAE then make the export process 

Since Import/Export laws keeps changing in the Gulf Countries, you need to check with U.A.E. if they have no restrictions on imports via Saudi Arabia Terminals. But in general I don't see any problem if full documentation is available.

I am not much aware of it, however, if KSA & UAE have any trade agreement for such trans shipment then it is possible.

Yes Possible .. 

1. Required commercial export license 

2. Arabic commercial invoice + certificate of origin + Packing list + Certificate for re-report Goods 

3. Attested from Chamber of Commerce 

4. Authorization letter to transporter ( legalized by clambering)

5.Customs declaration online + duty payments in border

If I missed something - please let me know the things