Abstract: Velocity of quench front is one of the important parameters which measure the cooling efficiency of the reactor core during the reflooding process after loss of coolant accident. Based on an experimental study of propulsion characteristics of quench front in a vertical annual channel, the effects of initial clad temperature, inlet coolant temperature, inlet mass flow flux, and heating power on the velocity of quench front were investigated. The results show that the velocity of quench front decreases with the increasing of the initial wall temperature, inlet coolant temperature as well as heating power, but increases with the increasing of the inlet mass flow rate.