The state of Kermanshahs during the Qajar period extends from the west to the Baghdad state, from the south to the mountains of Lorestan, from the north to the Kurdistan state, and from the east to the province of Hamadan, whose people speak the Kurdish language. This state can be considered one of the important bases of Twelver Shiism in Iran. Human factors have played a major role in the formation of the intellectual foundations of Shiism among the people of this region. During the Qajar era, the Shiite religion successfully passed an important phase of its intellectual and political life. Therefore, the main question of the current research is which human factors have played a role in the spread of Shiism and its institutionalization among the people of Kermanshah province? The influence of the Shafi'i religion, the role of Sufism, the emphasis of the Qajar rulers on strengthening the Shia religion, the efforts of the Shia merchants, the role of the Shia scholars in enlightening and proving the truth of the Shia religion, the effect of the Shia manifestations and the role of the love of the Ahl al-Bayt in the tendency of the people to the Shia religion are among the most important. The factors of entry and expansion of Shiism in Kermanshah province