Abstract: The bubble behavior of subcooled R-12 flow boiling in the narrow channels with both double-side and single-side heating was studied experimentally.Experimental settings are: a test-section heating length of 400 mm,a cross-section of 35 mm in width and 2mm in gap size,a mass flux of 700～1500 kg•m^-2•s^-1,a heat flux of 25～70 kW•m^-2 and a pressure of 1.3～2.0 MPa.A comparison was made in terms of the onset of nucleate boiling(ONB)point and bubble characters with other flow pattern. The study found that with some appropriate modifications, the characteristics of double-side heating and single-side heating showed a better similarity.