There are so many views about the author of Mahabharata. Following views have been put forward regarding the authorship of Mahabharata:
It is believed that the original story was written by the charioteer-bards known as Sutas. They originally accompanied Kshatriya warriors to the battlefield and composed poems celebrating their victories and other achievements. It is also believed that the beginning text of Mahabharata was orally circulated. Scholars and priests carried it from one generation to another.
From the 5th century BCE, the Brahmanas took over the story and started writing. This was the time when Kurus and Panchals were gradually becoming Kingdoms. This story of Mahabharata also revolved around them. Some parts of the story reflect that old social values were replaced by the new ones. c. 200 BCE and 200 CE is another phase, In the composition of the Mahabharata. During this period worship of Vishnu was gaining ground. Krishna came to be identified as Vishnu.
Large didactic sections resembling Manusmriti were added during the period between C 200 and 400 CE. These interpretations made the Mahabharata an epic consisting of 100,000 verses. This enormous composition is traditionally attributed to a sage named Vyasa.