||The newly released refine option of Open Access on the Web of Science platform makes it possible to analyze the article-level OA content across the whole Web of Science database, including more than sixty million documents. In this study, employing the OA filter option of Web of Science, we perform a large-scale evaluation of the OA state of countries from 1990 to 2016. Particularly, for each country, we consider not only the absolute number of Gold OA literature but also the ratio of them among all literature. We compare the rates and evolutions of OA across countries. Our results show that the number of OA articles have increased quickly in the last decades. Currently, one quarter of the Web of Science articles are Gold OA articles; In contrast, in 1990, the percentage of OA articles is less than 8%. Brazil is found to be the most active country in OA publishing. In contrast, Russia, India and China have the lowest OA ratios. In addition, the temporal trend analysis shows that the OA percentage of Brazil has been decreasing dramatically in recent years, while the OA percentages of China, UK and Netherlands have been increasing.