Abstract: The initial ice jam thickness is a basic parameter in research of ice jam character and has important influences on its thickening, developing or in equilibrium later on. In this paper, flume experiments on the formation of initial ice jam thickness and its varying mechanism were carried out, brought to light the relations between factors of initial ice jam thickness, flow condition and ice discharge etc.. Experimental results revealed that it is feasible to use paraffin instead of ice in flume experiments to conduct qualitative researches on the formation and developing mechanism of ice jams.