###### Abstract  
Patents as proxy for technological trends is well noted. The rapid increase of patents in China, however, has aroused debates on its technological progress: 'few original innovations' are produced in advanced areas, and true 'breakthroughs' are disproportionate to the quantity of the applications. As different technological fields contributions vary to technological progress, a nuanced understanding towards technological composition is in need to help reveal China's strength in technological innovation. This research takes the Yangtze River Delta (YRD), one of China's most inventive city-regions, as an epitome to examine the issue via three steps: (1) valid patent inventions applied from 2010 to 2018 are sorted to capture the concentration and colocation features of 35 technological fields defined by the World Intellectual Property Organization (WIPO); (2) four types (intensive, extensive, distinctive, and supportive) of technologies exemplifying technology intensity and interactivity are identified by the cross-classification method and further analyzed by spatial autocorrelation; (3) how urban factors relate to innovation of these four types of technologies are explored. This research unveils a mixed but polarized structure of technological composition in the YRD where the spatial concentration of technologies is as analogous to the nation's but colocation is not; though quite a few technologies fall into the intensive (usually high-tech) category which assumes to be more likely to breed 'breakthroughs', their numbers are limited and far less than extensive (usually labor intensive) or supportive. Knowledge exchange is frequent in core inventive cities where economic performance measured by GDP is most eminently linked to patent inventions of categorized technologies, the exception is intensive technology for which the significance of university students overrides other factors. Extant research contends that knowledge spillovers are geographically bounded and that technology breakthrough as well as economic benefits are gained within this boundary. A populated city-region is considered as a spatial scale fitting such boundary for innovative activities [12; 13]. Scale effects produced by city-regions help minimize externalities by sharing earns and risks that are brought about by technological or industrial specialization, reduce transaction costs through efficient resource, labor, and goods search, and foster active learning and exchange of tacit knowledge [14; 15; 16]. It is also a scale reaching the limit of knowledge spillover and tacit knowledge exchange, thus most likely to breed primary invention [17; 18; 19]. Yet, as city-regions differ in location, resources, and governance systems, how knowledge creation activities distribute in different fields and spatially interact within a city-region are considered case-by-case and far less understood. Using patent data, some studies have conducted country-level analyses to reveal the composition and spatial location of technologies, mostly in U.S. and Europe [17; 20; 21], but there have not been many efforts deploying patent data to deconstruct technological composition within the city-region. Patent filing in China has grown rapidly over the past years since the pursuit of innovation strategy. Taking advantage of the large set of patent data, studies on China's innovation landscape have emerged around 2010 [22; 23; 24; 25; 26]. The findings suggest that innovative activities are spatially concentrated in coastal areas, particularly the three most populated city regions (Beijing-Tianjin-Hebei, Yangtze River Delta, and Pearl River Delta) with very small portion engendered outside, and that the degree of spatial concentration of innovative activities in China far outweighs that in the U.S. and EU [27]. Therefore, the key to understand technological innovation in China would be to decipher the innovation landscape in the coastal, populated city-regions.