During the special action of land reclamation (land-control act) in city Z of province A, some Christian churches were identified as "illegal constructions". Based on the field-research materials gathering from these "illegal" churches in city Z, this article applies "belief pattern (Xinyang Fangshi)" as the core concept to analyze motivations and operations in the establishment of local Christian churches, and discusses the interactions between local government and Christians in this process from the perspective of "land rules". It can be inferred that the "Church", as an important element in the local belief pattern, which was objectified during construction and finally led to the "Church Building Fever", is the antecedent cause of these illegalized churches. Through the comparative study of four typical "illegal church" cases, this article demonstrates that the religious land use has adopted informal institutions and resulted in the suspension of formal system and involution of local government, along with the "conspiracy" or "co-opetition" between government and Christian churches for shared interests, all fostering the springing-up of "illegal churches" in varying degrees. In summary, a series of problems regarding "illegal churches" indicates the lack of public order in a local society.