Abstract: Taking Shenzhen city as study area, on the basis of the gravity two-step floating catchment area method(G2SFCA) considering the distance attenuation effect, the Huff arithmetic, demand point location as well as terrain were introduced into the model. G2SFCA was improved from three aspects:competition of supply point, location of demand point and optimization of road network distance. An improved G2SFCA is proposed to study the spatial accessibility of indoor emergency shelter in Shenzhen city. Experimental results show that the improved G2SFCA can not only reveal the indoor spatial accessibility of emergency shelter in various communities of Shenzhen city, but also effectively reflect the spatial matching law between accessibility and population density distribution, which is more realistic than other models. The results of statistics and analysis on the quantity, population accommodation and spatial accessibility of indoor emergency shelters are true and reliable. The relevant conclusions can be used for reference for future disaster prevention work and space planning of indoor emergency shelter in Shenzhen city.