Abstract: Based on the event every year for selecting the annual important advances about science, technology and engineering held by the Editorial Department of Science and Technology Review Publishing House, with the principles of evaluating within each branch, our journal recommendation, experts selection, putting quality before quantity, and giving facts in time order, 10 important scientific achievements, 10 important technological achievements and 10 important engineering achievements in China in 2009 were selected by relevant experts and scholars, based on candidate items recommended by our journal, which originated from a lot of scientific news in the columns "Sci-Tech News Ranking for the Half-month", "News Round", "Domestic News Briefs", "Domestic Journal Highlights", "Scientific Community Briefs", "Events" and "Cover Story" in Science and Technology Review, and key academic journals and scientific newspapers. These achievements included the discovery of the maximum strength in nanotwinned copper and ultra-high strain hardening effect, deficiency of a β-arrestin-2 signal complex contributes to insulin resistance, a pressure-induced transformation of sodium into transparent insulating states, running test of the domestic first practical middle-low speed maglev train, the global first practical prototype of nanosecond solid-state deep UV laser source has been successfully developed, the world's largest diameter large field optical astronomical telescope has been built, successful trial run for megaton demonstration project of Shenhua coal direct liquefaction, completion and operation of the domestic first UHV AC Power transmission and transformation project, moon-landing success for Chang'e-1 and perfect ending of the first phase project of China's lunar exploration, etc.