The discussion on innovation networks of patents or papers has attracted many economic geographers; however, the Industrial Technology Innovation Strategy Alliance (ITISA) has been ignored, although it is also an important innovation form of firms, and the formation mechanism of alliance innovation networks is unclear. This study is based on the data of Shanghai high‐tech ITISAs between 2010 and 2015, and employs the methods of social networks and negative binomial regression to analyse the actor structure, spatial structure, and proximity mechanism of innovation networks of Shanghai high‐tech ITISAs. Results highlight the following: (a) Firms comprise the largest number of actors in alliance innovation networks, and universities, research institutions, and industry associations also play some roles. (b) The local and rooted characteristics of the innovation networks of ITISAs are obvious. The spatial distribution of innovation partners is mainly in Shanghai, and a few innovation actors are located in neighbouring cities, such as Suzhou, Hangzhou, and Ningbo in the Yangtze River Delta Urban Agglomeration. (c) Proximity significantly promotes the formation of innovation networks in an ITISA and contributes to the improvement of innovation ability, and organizational proximity plays a greater role than geographical proximity or cognitive proximity.