The Ghana captain is understood to be undergoing a medical today with Jaap Stam's side ahead of a temporary move to England's second tier.
It will be Gyan's second spell in England after spending a year-and-a-half at Sunderland where he played 37 times and scored 10 goals before making a controversial move to the Middle East.
Gyan joined Shanghai SIPG last year in a move that saw him become one of the world's best paid players at the time.
It is thought that the majority of the striker's wages will be paid by his parent club when he finally completes his loan move to Reading.