Both visual technology and numerical simulation were employed to investigate bubble jet flow formation during boiling of subcooled water on ultrathin platinum wires. Experimental observations and measurements indicated that bubble jet How formation could be typically divided into three stages: waiting, burst and stably developing stage. A transient numerical model was proposed to simulate the formation process accounting for the thermocapillary force existing at the bubble interface. The dynamical temperature variation in the liquid region, including the regions of the mushroom head and root stem, were numerically analyzed, showing a very good agreement with the experimental observations. The simulation very well explored the physical nature of the dynamical evolution of bubble jet flows and explained the experimental phenomena. ((C) 2007 Published by Elsevier Ltd.