The investigation of real estate ownership refers to finding out the status of real estate units composed of parcels, zonghai and their houses, trees and other fixtures, including parcel information, zonghai information, houses (buildings) information, forests and trees information. Real estate ownership survey includes real estate ownership survey and real estate measurement. At the time of registration, the real estate registration agency shall examine the results of the survey of real estate ownership, including "whether the results of the survey of real estate ownership such as boundary, spatial boundary and area are complete, whether the ownership is clear, whether the boundary is clear and whether the area is accurate", and take the results of the survey of real estate ownership such as the ownership questionnaire as the necessary materials for applying for registration. Real estate ownership survey is the basic work of real estate registration, and the data of ownership survey results have legal effect after real estate registration. On the basis of cadastral survey and parcel, investigating the ownership of fixed objects such as land, houses and trees can avoid problems such as overlapping rights and asymmetric information that may arise due to different investigation basis, which is conducive to protecting the legitimate rights and interests of obligees according to law.