With the rapid development of economic society and urbanization construction, urban space resources are becoming increasingly tense. As a hub of economic development and external communication, coastal cities have more urgent needs for urban space resources. At the same time, due to the multiple impacts of the marine environment, the suitability evaluation of underground space development is more complex and important. However, at present, there are few studies on the suitability evaluation of underground space in coastal areas. The evaluation index system is very different from that of inland cities. The evaluation method of subjective and objective combination weighting is becoming more and more perfect. The influence and scientificity of different methods on the suitability evaluation of underground space need to be discussed.Methods: Taking the coastal area of Weibei Plain in Weifang City as the research background, four different subjective and objective combination methods of improved structural CRITIC, game theory, minimum relative information entropy and multiplication synthesis method are used to empower, and based on ArcGIS spatial analysis function, the suitability of underground space development in the study area is comprehensively evaluated and compared.Results:① The calculation results of different subjective and objective combination weighting methods show that the four indexes of fault structure, groundwater richness, groundwater depth and permeability of rock and soil layer have significant influence on the suitability of underground space development. ② The improved structural CRITIC, minimum relative information entropy and game theory have good correlation, and the correlation coefficients are 0.9825, 0.9585 and 0.9093, respectively, which can scientifically reflect the subjective and objective weights of each evaluation index. ③ The sum of very suitable and suitable areas accounted for 44.13 %, 42.87 %, 41.35 % and 42.53 % of the total area in the suitability evaluation results of underground space development in coastal cities based on different combination weighting methods. ④ The areas that are very suitable for underground space development are mainly concentrated in the Shuangwangcheng Ecological Economic Park in Shouguang City, the west of Yingli Town, the middle of Gudi Street in Hanting District, the west of Zhuli Street, and the intersection of Longchi Street, Kuiju Street and Duchang Street in Changyi City.Conclusion:Four different subjective and objective combination methods reflect their own characteristics, which have certain guiding significance for the development of underground space in coastal cities. In the actual urban geological work, the corresponding combination weighting method is selected according to the scene, data acquisition difficulty, decision-making environment and other factors.