Galle stadium curator Jayananda Warnaweera said the early-November deadline for reconstruction would be met.
The stadium, originally the venue for the opening match of a three-Test series against England, will now host the third game. The first Test will be held at Kandy and the second at Colombo.
"We took the decision to host the third Test to gain a couple of more weeks so that work on the pavilion could be completed," Warnaweera told AFP.
He said the new pavilion would include ultra-modern facilities for both players and spectators and be better than it was before the December 2004 tsunami struck.
When completed, the stadium overlooking the colonial-era Galle Fort and the Indian Ocean will accommodate 20,000 spectators, up from its original 15,000.
Galle, 112 kilometres (72 miles) south of Colombo, is a happy hunting ground for Sri Lanka who have won six of their 11 Tests at the venue.
"We have made new wickets and they are ready for use even today", said Warnaweera, also a former Test spinner.
England will play five one-day internationals in Sri Lanka in October, with Dambulla hosting the first three matches and Colombo the last two. They then return home before coming back for the November Test series.