Before understanding the advent and spread of Christianity in India, it is necessary to understand what religion are Christianity.What are its basic ideas? Therefore, first of all, the basic ideas and history of Christianity will be presented briefly, because the correct way to understand a religion is to understand it directly from the people of the religion, so it will be an attempt not to attribute anything to Christianity without reference to Christian scholars themselves, and since the purpose of this is only to understand Christianity, No theory of religion will be commented upon, but only information related to its basic ideas and history will be discussed, and studying Christianity by Muslims in the subcontinent, it is important to know how Christianity reached the subcontinent and then how it established its foothold in this area and how it achieved so much progress here. In the beginning of the year, Alexandria was the largest trading city in the world, Indian merchants who went to Alexandria to trade silk and pearls, and on their return brought with them a collection of books of Mustan to India. In the early 2nd century, some Indian merchants wrote a letter to Bishop Demetry Youss of Alexandria, asking him to send a capable man to India for the tabalgar mastay, so he sent the Pontius priest, who was one of the most capable people of his time; to India and that he was the "first missionary" in India. How the British spent their energies in the spread of Christianity in the subcontinent and adopted every means that could promote Christianity, from the army of priests and missionaries to the misuse of government power and from books to magazines and newspapers and from public preaching to debate, they adopted every method by which Christianity could be spread. But Muslim scholars also continued to observe this whole situation closely and they not only closed the siege in front of the growing storm of Christianity on every front in defense of Islam, but also reined in this vicious ness and held it in such a way that they did not give it a chance to rise again.