Abstract: An experimental investigation was conducted to visually observe nucleate boiling phenomena in wedged gaps.A flat and uniform copper plate was used as a heater.The surfase of copper plate was ground by polishing method in order to reduce rugosity.A glass plate was used as a sheet for forming a wedged gap in the experiments.Ethanol was the object for observing and measuring.The phenomena showed that boiling nucleation favorably occurs and bubble growing is faster in areas with larger space in narrow gaps.The nucleation on the surface in relatively narrow zone was more difficult and needed higher heat flux than that in larger space zone.Images and figures shot by CCD camera were used to record bubble growth processes.It is observed that nucleation and bubble dynamical evolution in the same gap spacing zone are identical and the growth rate was maintained at a constant value for ≥0.1.