Study on the 392 Catholics in 4 parishes in Hanoi, in-depth interviews with 10 priests, monks, teachers and 20 followers and interview 4 typical cases on objective factors influence on prayer behavior of believers shows that, according to the assessment of the news, the elements of family and group elements from Catholicism have a strong influence on the prayers' behavior; in which family factor group seems to have a stronger influence. However, in the group of elements from Catholicism, the element of Catholic teaching about heaven, the role of God and the Bible, the doctrine is most appreciated for the degree of influence, even higher than the elements of the family group.