Although he never published his view on the subject, according to a book called "Slavery and Sin: The Fight Against Slavery and the Rise of Liberal Protestantism" By Molly Oshatz, Edwards was just slightly opposed to slavery in that he questioned the slave trade as it was existing and practiced, while not opposing the concept of having a slave if recognizing them as equal humans and if they had fallen into the state of slavery through some legal means. We know his view only from his arguments for and against slavery in his defense of Benjamin Doolittle, a pastor who was criticized by his own congregation for owning slaves.
Slavery was only beginning to become a moral issue in Puritan New England at the time of Edwards. This was not really America but England and Edwards as good hearted as he might seem from his sermons was still part of a ruling British mentality that did not seem aware of the concepts of full economic opportunity that we understand under the word equality today and as promoted by modern democracies in many parts of the world.
It might seem contradictory but although he did have a slave/s he was also somewhat opposed to slavery even back then. He did not take a stance against slavery as 'always' wrong, for he saw that the Bible itself does not even mandate, even in the New Testament, that Christian slave owners in the church must free their slaves, but he did personally begin to oppose the 'racial' slave trade and its philosophy of 'human inequality'. His opposition to slavery was only starting to dawn, even while he had his own slave, based on what he thought was an unjust practice of enslavement. In other words, he questioned the means that people were brought into slavery. It would seem if he lived just a little later in history common sense would have extended this soft opposition to a more aggressive form, but I guess we will never know for sure.
A fuller description can be found here Slavery and Sin: The Fight Against Slavery and the Rise of Liberal Protestantism and here Jonathan Edwards, Slavery, and the Theology of African Americans.