In order to understand the effects of endplate thickness, bolt diameter, bolt pretension, thickness of column flange, steel grade of endplate and fire temperatures on the behavior of high-strength steel beam-to-column endplate connections, a design concept that thin high-strength steel plate is used to replace the general thick steel plate is deeply discussed, and this paper presents a parametric analysis by using finite element modeling. The results presented herein show that with the increase of the endplate thickness, the initial rotation stiffness and peak moment increase, but the rotation capacity decreases. With the increase of the bolt diameter, the initial rotation stiffness, peak moment and rotation capacity increase. With the increase of the bolt pretension, the initial rotation stiffness increase, but no difference of the peak moment and rotation capacity occurs. With the increase of the column flange thickness, the initial rotation stiffness decrease, but the peak moment has no difference and the rotation capacity slightly decreases. With the increase of the steel grade of the endplate, the initial rotation stiffness remains, the peak moment increases and the rotation capacity remains when the steel grade of the endplate doesn't exceed Q460, while the rotation capacity decreases observably when the steel grade of endplate exceeds Q460. A proper design using a thinner high-strength steel endplate can achieve the similar load-bearing capacity and comparable or even higher rotation capacity, in comparison to a connection with thicker mild steel endplate, no matter at ambient temperature or after fire. Further, the failure mode of the endplate connections may be changed after fire, even from a ductile failure mode to a brittle failure mode.