As for the sinicization of foreign religions, the academic circle has summarized and studied the positive experience of the four existing religions:Buddhism, Islam, Catholicism and Protestantism. From a new perspective, this paper studies the three foreign religions disappeared during the mediaeval times, that is, Zoroastrianism, Manichaeism and Nestorianism. By analyzing why they failed to spread in China and comparing the practices of Buddhism and Taoism, this paper also illustrates that it is necessary to adhere to two basic principles of "maintaining the country's stability and improving people's welfare" in the sinicization of foreign religions. Otherwise, foreign religions cannot exist in China for long.