China launched its national emissions trading scheme (ETS) in late 2017. This article examines the key drivers behind China's 2011 decision to opt for ETS as a GHG mitigating policy tool and what lay behind the choice of the system's design features. Given the existence of the frontrunner EU ETS and that market mechanisms have spread across the world in recent years, we analyze the role played by policy diffusion in the decision to launch an ETS and in the subsequent design process, seen in relation to domestic drivers. The article investigates policy developments culminating in the 2011 carbon market announcement, and the reasons these design elements were chosen for the pilot schemes and the national market in the period 2011-2017. The article contributes to our understanding of policy diffusion at different stages of policy development in China, by revealing which diffusion mechanism is more prevalent at different stages. We find first that overall domestic conditions and drivers had the most consistent impact on policy decisions to establish a carbon market and on the selected sectors. However, a second key finding is that the role of policy diffusion varied over time, with such diffusion, in the form of ideational impact, playing the most important role early on, providing a powerful inducement for China to go for a carbon market. Third, sophisticated learning from international projects took place in the pilots, allowing China to adapt policies and design features to match local conditions.