This article aims to explore John Wesley’s position upon the slave trade and slavery in England of the 18th century and his influences on the campaign for ending the slave trade and slavery. John Wesley, as a leader of awakening movement, was concerned with the personal conversion and the revival of faith and church. Regarding his social and political position, he as a Tory was royal to the english monarch and was against American Independence. Accordingly, he has been seen as conservative in terms of social perspective. It has sometimes caused the speculation that John Wesley was not interested in ending the salve trade and slavery, which is one of the greatest atrocities of civilization at his times. That is the case with the founder of North American Liberation theology and a leading Methodist theologian, James Cone. It is really ironic that he wrote, “The Wesley that has come to us seems very white and quite British, and that ain’t no good for black people who know that the Englishmen are the scoundrels who perfected the slave trade,” and indicated, “one does not get the impression that slavery was one of the burning issues on Wesley’ mind.” Actually, the early mission to Georgia in America brought John Wesley into direct contact with black slaves there. Since then, his concern about the slave trade and slavery had not disappeared in his mind, even though he more concentrated himself on the revival movement ignited by his own conversion. We can find out his criticism upon the slave trade and slavery in his Journals and Diaries, letters, and his Writings. Especially, his tract “Thought upon Slavery,” which partly drew on some writings by Anthony Benezet and Granville Sharp, had a great influence upon the methodists and mass. In his small book, he harshly criticized the slave trade and slavery itself as sum of all inhumane evils. His criticism was based not only on the Bible, but also on the general natural law and justice. Besides, he encouraged some leader of antislavery campaign to continue to do his action. Among these was included William Wilberforce, who spent a lifetime passing the bill for abolishing the slave trade and slavery through Parliament. After death of John Wesley, his follower and methodists still supported William Wilberforce to achieve his goal.