The aim of this work is to optimize process design parameters of the hot rolling steel strip preposition ultra-fast cooling (UFC) system, and improve the stability and uniformity of micro heat transfer during the high strength cooling process of hot rolling strip. According to the technology and equipment feature of the pre-UFC system for a factory, the convective heat transfer process of single nozzle and strip in UFC system was studied numerically by the fluid-structure interaction finite element method (FEM). The influence of different parameters on the slot impinging jet heat transfer coefficient was obtained, such as jet angle, the jet velocity, the slot nozzle width and water temperature. The results show that on the ultra-fast cooling process of the strip in the initial temperature of 850 °C and thickness of 8 mm, the global average heat transfer coefficient can be increased with the increase of jet velocity, and decrease of the cooling water temperature. The jet angle and the slot nozzle width have minimal effect on it for the whole heat transfer zone. The local average heat transfer coefficient first increased and then decreased with the increase of jet angle and slot nozzle width at the jet impingement location.