The processes of Chinese urbanization are characterized by both horizontal expansion and vertical growth of buildings. Compared with urban surface expansion, urban height rising seems particularly important for sustainable urbanization. The vertical increase in buildings is helpful to reduce using land resources that are scare in China, and can contribute positively to the optimization of urban landscape structure and urban functions. Estimating and measuring building height has become one of the most significant factors in urban planning, urban expansion, urban disaster warning and assessing, as well as providing initial mapping data for creating three-dimensional (3D) digital city models. This paper reviews the methodologies of extracting building height, making use of various optical remote sensing images, VHR (Very High Resolution) SAR images, and the fusion of optical images and VHR SAR images. Then we summarize the advantages and disadvantages of the three techniques. When optical images are available, the shadows of buildings are often used to calculate building height. The accuracy of this technique varies tremendously depending on algorithms. Supervised classification method and edge detection method were widely used in recent years. In addition, the volumetric shadow analysis and areal shadow analysis also become more and more popular. If SAR images are available, the use of single VHR SAR image is an effective way to extract building height. Radar interferometry method, stereo-pair method, and quantitative analysis in electromagnetic intensity of backward scattering are also commonly used. Either optical or SAR images has its drawbacks for extracting building height. As a result, the fusion method that integrating optical images and SAR images are adopted, and it proves to be an accurate way of building height extraction. Apart from the accuracy of calculating building height, we need to take the other important elements into account, such as cost, complexities and application ranges in practice. Based on the comparisons of the three techniques mentioned above, we can also summarize the temporal progress in researches on building height extraction in the past decades and analyze the trend of future technical development in building height detection. With the improved monitoring methods, accumulated experience and innovated technologies, a low-cost, practical and accurate method on extracting building height will be found out in the near future. At last, paying more attention on building height also means paying more attention on urban height, and the expansion of urban height has an important effect on city's 3D expansion. For one thing, the vertical growth of cities is good at easing urban horizontal expansion pressure. For another, the increases in building height make it possible for maintaining city's compact spatial form.