By collecting and sorting the relevant data from 2001 to 2017, a preliminary study on the rules and influencing factors of red tide outbreaks in offshore areas of China was conducted. The results indicate that the occurrence pattern of red tide in the offshore areas of China increased firstly and then decreased. The area and frequency of red tide in China seas increased significantly from 2001 to 2005, while decreased significantly from 2006 to 2017. From 2008 to 2017, a total of 608 red tides occurred in China, and 65 species were the first dominant species that triggered red tides. Prorocentrum donghaiense was the organism that caused the most red tides, 106 times totally. The influencing factors of red tide in each sea area were different: the changes in red tide area in the Bohai Sea were mainly affected by nutrients and total nitrogen; the changes in area and frequency of red tide in East China Sea were significantly affected by nutrients, total nitrogen, total phosphorus, and nitrite nitrogen; the changes in the area of red tide in South China Sea were significantly positively correlated with pollutants entering the sea and CODcr (P<0.05). In order to further reduce red tide outbreaks, several suggestions were proposed for prevention and control of red tide in offshore areas of China: establish online monitoring stations; take control measures based on local conditions; strengthen source pollution management; improve emergency response systems; carry out marine ecological restoration.