Abstract: The flow and circulation of low-carbon technology knowledge is an inherent requirement for building a new pattern of "dual circulation" and promoting sustainable economic growth under the "dual carbon" goal, but there is a lack of domestic policy research. Based on the balance panel data of 218 prefecture-level cities in China from 2006 to 2019, this paper reflects the overall flow of low-carbon technology knowledge with patent information, and uses the multi-point DID method to empirically test the impact and mechanism of low-carbon city pilot policies on low-carbon technology knowledge flow. The results show that: (1) The low-carbon city pilot policy can effectively promote the flow of low-carbon technology knowledge in general, but it is mainly manifested in accelerating the inflow of low-carbon technology knowledge. However, it has not shown the effect of the pilot policy on the spillover of low-carbon technology knowledge. This may be related to the insufficient demonstration effect of pilot policies. (2) Pilot policies can promote the knowledge flow of gray and clean technologies, but they have a more significant effect on gray technologies with more gradual and incremental characteristics, which is contrary to the reality that clean technology knowledge flows very quickly. (3) A higher level of human capital and industrial structure in pilot cities will help strengthen the promotion role of low-carbon city pilot policies, and the policy effects will be more obvious in the eastern and central regions, first- and second-tier and non-resource-based cities. Therefore, we should actively promote the demonstration and expansion of low-carbon city pilots, activate clean technology activities, and try to adopt differentiated pilot policies; The eastern and central regions and major cities should give full play to their existing talent and industry advantages, actively support the development of clean technology, and lead the deep low-carbon transformation; The western region, small and medium-sized cities, and resource-based cities should pay more attention to the coordination of pilot policies with other policies, so as to form a policy synergy to promote knowledge flow.