N. Dorjee, secretary of the Bodh Gaya temple management committee, said work on the dome started in November. A Thai company carried it out, overseen by the Archaeological Survey of India (ASI).
The gold was flown in a special plane from Bangkok.
Dorjee said it was Thai King Bhumibol Atulya who decided last year to cover the temple dome with gold. But it took time to get the ASI's clearance.
The first phase of the work involving chemical treatment was completed in August to prepare the foundation for gold plating.
The ancient 180 feet structure of the Mahabodhi temple is estimated to have been built between the 5th and 6th century AD.
It was lost and rediscovered in the 19th century by Alexander Cunningham, who founded the ASI in 1861.
