Extremely large telescopes with more and more large apertures are pursued, proposed and constructed by astronomers and technicians all over the world in the coming next years to satisfy the great demand of scientific progress. Segmented mirror active optics is the most important technology to co-phase the large primary for optically perfect segmentation. Based the experimental platform and test work in Nanjing Institute of Astronomical Optics and Technology in China, we introduce the latest co-phasing progress on fine segment support, edge sensor and close-loop co-phasing correction in China in this paper. Finally some conclusions are given based on the test results.