Ocean acidification is a well-known global issue. This study aimed to reveal the trends in research on ocean acidification. We used the method of bibliometric analysis to review the literature related to the study of ocean acidification published after the concept of ocean acidification was put forward(i.e., after 2004) and indexed ISI Web of Science journal citation database. We first created descriptive statistics of the number of articles published annually and the journal frequency distribution. Then, the methods of keyword-based knowledge mapping and burst analysis were used to explore the hotspots of ocean acidification studies and the recent frontiers. Descriptive statistics suggested that the number of studies on ocean acidification has increased sharply in the past ten years and that studies related to this issue had an obvious characteristic of being interdisciplinary. In addition, the influence of ocean acidification on coral reefs was a major focus of these studies in the past ten years. The keyword-based knowledge mapping showed that major studies on ocean acidification mostly belonged to the field of biology:during the initial stage of ocean acidification studies(2004-2009), the research contents could be mainly divided into two parts; one is the influence of ocean acidification on marine organisms(especially coral reefs and marine phytoplankton) and ecosystems, and the other is the mechanisms of ocean acidification. During the midterm stage(2010-2015), the research contents were similar to those of the initial stage. However, the focus of research was mostly shifted to marine organisms. In addition, this stage showed the emergence of new research areas and directions. In the recent stage(after 2016), studies on the influence of ocean acidification on marine organisms still form the primary research direction. Results of the burst analysis of the most recent(February 2018) literature hotspots showed that the current research on ocean acidification has five study frontiers:(1) combining other factors with ocean acidification to explore its relationship with marine organisms;(2) exploring the internal response mechanisms of marine organisms when they stay in an acidic oceanic environment;(3) comprehensive assessment and prediction of biological responses under the effects of ocean acidification;(4) exploring the impacts of ocean acidification on the marine ecosystem; and(5) challenges to the concept of ocean acidification and exploring other causes of ocean acidification.