###### Abstract  
Estimating the housing vacancy rate (HVR) has always been a hard-to-break point in the study of housing vacancy. This paper used nighttime light and POI (point of interest) data to estimate the HVR in the main urban area of Xi'an city based on extracting built-up areas. The built-up area was extracted using the threshold method, and the spatial resolution of the results was 130 m (same as Luojia-1). Meanwhile, after removing the non-residential areas from the images, the HVRs for the period 2018-2019 from four nighttime light images were calculated, and the HVR of the main urban area of Xi'an city was estimated using the average method and its spatial patterns were analyzed. The results show that: (1) Luojia-1 has great advantages in estimating urban HVRs. The HVRs calculated by Luojia-1 were characterized by a high resolution and a short calculation time. (2) After estimating the results of the four scenes' remote sensing images, it was found that the results obtained using the average were closest to the actual vacancy situation, and the spatial distribution of the vacancy could be seen using the minimum values. (3) The overall housing occupancy in Xi'an city was good, and the HVRs were low, but the overall vacancy rate for the edge of the built-up area was high. The government should devote more attention to places with high HVRs. h o 2022122328 20221222122212221  
housing vacancies are missing, the data are not disclosed, and the real estate industry is not transparent, resulting in the study of housing vacancies being very underdeveloped [10; 11]. On the one hand, there are different opinions in society regarding the implementation of the housing vacancy tax, as it lacks strong supporting evidence. On the other hand, there is a lack of research data and methods. The study of housing vacancies is conducive to understanding the spatial patterns and dynamic changes in the current real estate market, calculating the HVR from the perspective of geography [12], and providing a reference for the government to formulate regulatory policies and future development plans for the city. Over the past decade, there have been much controversy and advocacy in academia regarding housing vacancies. In terms of the definition of vacant housing, [PERSON] and [PERSON] [13] argue that a vacant house is a home that satisfies the need for unused housing and is planned to be rented or sold. The American Federal Bureau of Statistics defines a vacancy as a house that is uninhabited and not temporarily uninhabited at the time of the statistical survey, and a house that is inhabited or whose inhabitants are temporarily out of the country at the time of the statistical survey is defined as a house in use. The \"2017 China Urban Housing Vacancy Analysis Report\", released by the Southwestern University of Finance and Economics, divided vacant houses into two types according to the number of houses owned by housing families: a single suite owned by a family was vacant because of leaving to go to work; multisite family homes that were neither inhabited nor rented [14]. In this study, we defined a housing vacancy as a house that has been unoccupied for a period of time, whether rented or sold, and thus vacant. This definition implies that a housing vacancy is a persistent state rather than a state at the point in time of an investigation [15], emphasizing the continuity of the state. From the perspective of the development of the real estate, the reasons that affect housing vacancy mainly include market supply and demand factors that lead to a mismatch between housing supply and housing demand [16], functional housing factors that do not allow for normal living due to the presence of defective housing functions [17], and speculative factors that lead to the purchase of multiple houses to maximize profits [18]. However, it is difficult to assess housing vacancies from the same perspective due to the different architectural structures and cultures in China.