The extracts of the study by defense consultancy IHS Jane’s were published on Monday in The Daily Telegraph.
IHS Jane’s estimates that some 10,000 militants are fighting for groups affiliated with al-Qaeda such as al-Nusra Front and the rest fight for different militant groups.
The analysis also said that a large number of extremists from foreign countries are also active in Syria.
Syria has been gripped by deadly unrest since March 2011. According to reports, the Western powers and their regional allies — especially Qatar, Saudi Arabia, and Turkey — are supporting the militants operating inside Syria.
According to the UN, more than 100,000 people have been killed and a total of 7.8 million of others displaced due to the violence.
Al-Nusra and other militant groups accuse Damascus of launching the August 21 chemical weapons attack which they claimed killed about 1,400 people.
The government has rejected the accusation, saying it has proof that the militants were behind the attack.