The investigation of hidden dangers of self-built houses is as follows: (1) Basic information of houses. A comprehensive survey of housing construction years, structural types, construction sites, property owners (users), construction methods, building floors and areas, land properties, housing uses, rural housing energy consumption patterns, etc. (2) Illegal buildings focus on unauthorized storey addition and illegal new construction, renovation and expansion, especially illegal renovation for business premises, and comprehensively investigate illegal construction and illegal change of housing use. (3) Building structural safety, mainly checking whether there are potential safety hazards in foundation, superstructure and rural prefabricated buildings; Safe use of the house, mainly check whether the house is in disrepair, change the load-bearing structure decoration, all kinds of external decoration and external insulation layer, decorative lines, billboards, veneers are in danger of falling off, elevators and other special equipment meet the safety requirements; Fire electricity and gas safety, mainly check whether the fire facilities are configured according to the requirements and can be used normally, whether the safety evacuation passages and exits are unblocked, whether the installation and use of electrical gas equipment and the laying and maintenance of lines and pipelines meet the requirements, and whether the catering places use bottled liquefied gas illegally; Whether the house site is safe depends mainly on whether the house is located in the geological disaster-prone area, whether there are potential safety hazards around the site and whether the slope is stable. The safety of building materials is mainly to check whether the house uses toxic and flammable building decoration materials and whether it uses unqualified building materials.