On July 3, 2019, a violent tornado, which was recorded by video in detail, occurred in Kaiyuan City, Tieling, Liaoning Province. Based on the detailed damage survey and video data, this paper presents the lifecycle, occurrence time, path, disaster width and intensity distribution of the tornado. It is found that the weakening or strengthening of the tornado intensity was significantly related to the underlying surface conditions of dense high buildings and open field areas. According to the comprehensive assessment, the maximum intensity of this tornado is Level 4 (equivalent to EF4 in the United States), but the distribution range of the Level 4 disaster was very small, and the disaster distribution width and the range of Level 4 disaster were significantly smaller than the EF4 tornado in Funing, Jiangsu Province in 2016. The main structure of residential buildings with reinforced concrete frame structure remained almost intact after striking of the tornado with EF3 intensity at least, while the defense ability of largescale steel frame plant to tornado disaster was far worse than that of residential buildings. The areas through which the powerfull tornado passed are mostly wilderness and factories. Fewer people were affected and there were good views when the tornado occurred, which is an important reason why the tornado did not cause more serious disasters. Due to the complexity of underlying surface conditions and disaster mechanism, there must be some uncertainty in the estimation of the tornado strength.