This paper discusses the research of British naturalists in China during the period between the Opium War and the collapse of the Qing dynasty (1839–1911). China was defeated in the Opium War and forced to open treaty ports for trade with the Westerners. The foreign powers, particularly Britain, imposed upon the Qing government treaties, concession leases, favourable trade conditions, legal privileges and so on to reduce its political autonomy. In the shadow of the informal empire, not only did the British have more freedom to travel in China, first at the treaty ports and later in the interior, but they successively established diplomatic, commercial and missionary institutions in dozens of Chinese cities. The most important of them – the British Consular Service, the Chinese Maritime Customs and the Protestant missionary organizations – provided the talent and infrastructure for natural historical research and became networks for scientific information. The research into China's natural history epitomized the characteristics of British research on China in general: it engaged in collecting and circulating an ever-increasing amount of information and aimed at producing ‘factual’ and ‘useful’ knowledge about China. The paper modifies current literature on scientific imperialism, which has dealt primarily with the colonial context, by examining the role of nineteenth-century British imperial science in the context of informal empire.