The low-carbon technological innovation is playing a vital role in climate change mitigation. This paper aims to investigate the development trend of low-carbon technologies in the world. Using the patent data, we estimate low-carbon technology levels of 72 economies during the period of 1990-2012 and 19 OECD economies during the period of 1960-2012. Then, we explore the convergence patterns of low-carbon technologies among different regions based on a nonlinear time-varying factor model. The main findings are as follows. We do not find evidence of convergence for the 72 economies during the period of 1990-2012. But the convergence hypothesis for the 19 OECD economies during the period of 1960-2012 can not be rejected. Through the clustering method proposed by Phillips and Sul (2007), some convergence clubs are also identified. Our findings stress the importance of worldwide low-carbon technology cooperation: accelerating technology diffusion across regions and promoting projects of technology transfer to regions with low technology levels.