After fire, residual forces and deformations are re-developed inevitably in steel structures, and it may cause more dangerous consequence than that in fire condition. Beam-column connections are very important parts for the whole structure. In order to reveal more information about high strength steel flush endplate connection, an experimental study on mechanical behaviour of high strength steel flush endplate connections was carried out. Seven flush endplate connections were tested after cooling down from 550°C. The final deformation, moment-rotation curves and failure mode of high strength steel flush endplate connections were obtained and compared with those of mild steel flush endplate connections. Moreover, the provisions of Eurocode 3 were validated with the test results. It is found that a thinner high strength steel endplate can achieve similar residual load-bearing capacity and comparable or even higher rotation capacity after fire, in comparison with a connection with thicker mild steel endplate. Meanwhile, the provisions of Eurocode 3 for plastic flexural resistance of endplate connections are applicable when used to predict the behavior of high strength steel flush endplate connection after fire.