[Purpose/significance] This paper aims at getting a comprehensive understanding for the quantity and OA ratio of OA papers, and making a preliminary evaluation of these papers. [Method/process] In this paper, we utilized Web of Science Core Collection as the data source and took the four dimensions: publication years, research areas, countries/territories and organizations. We investigated papers published in high-quality academic journals that recorded in WoS from 2002 to 2016. Then, we analyzed and interpreted the changes and trends of OA papers. Finally, we took Nature as an example and analyzed the quality of OA papers from the perspective of citation per paper and highly-cited papers proportion. [Result/conclusion] The number of OA papers in the world have been increasing year by year, especially in China. Chinese Academy of Sciences (CAS) is the institution which has the largest number of papers recorded in WoS, the number of OA papers took the first place in 2016, but the OA ratio still lagged behind major European and American institutions. The OA practice in the field of biological and medical sciences is superior to other research fields.